Patent Application
20120094873
This invention describes a system which relates to the generation of randomized libraries of ligand-binding protein units derived from proteins containing the so-called C-type lectin like domain (CTLD) of which the carbohydrate recognition domain (CRD) of C-type lectins represents one example of a family of this protein domain.
The C-type lectin-like domain (CTLD) is a protein domain family which has been identified in a number of proteins isolated from many animal species (reviewed in Drickamer and Taylor (1993) and Drickamer (1999)). Initially, the CTLD domain was identified as a domain common to the so-called C-type lectins (calcium-dependent carbohydrate binding proteins) and named “Carbohydrate Recognition Domain” (“CRD”). More recently, it has become evident that this domain is shared among many eukaryotic proteins, of which several do not bind sugar moieties, and hence, the canonical domain has been named as CTLD.
CTLDs have been reported to bind a wide diversity of compounds, including carbohydrates, lipids, proteins, and even ice [Aspberg et al. (1997), Bettler et al. (1992), Ewart et al. (1998), Graversen et al. (1998), Mizumo et al. (1997), Sano et al. (1998), and Tormo et al. (1999)]. Only one copy of the CTLD is present in some proteins, whereas other proteins contain from two to multiple copies of the domain. In the physiologically functional unit multiplicity in the number of CTLDs is often achieved by assembling single copy protein protomers into larger structures.
The CTLD consists of approximately 120 amino acid residues and, characteristically, contains two or three intra-chain disulfide bridges. Although the similarity at the amino acid sequence level between CTLDs from different proteins is relatively low, the 3D-structures of a number of CTLDs have been found to be highly conserved, with the structural variability essentially confined to a so-called loop-region, often defined by up to five loops. Several CTLDs contain either one or two binding sites for calcium and most of the side chains which interact with calcium are located in the loop-region.
On the basis of CTLDs for which 3D structural information is available, it has been inferred that the canonical CTLD is structurally characterised by seven main secondary-structure elements (i.e. five β-strands and two α-helices) sequentially appearing in the order β1; α1; α2; β2; β3; β4; and β5 (
As noted above, overall sequence similarities between CTLDs are often limited, as assessed e.g. by aligning a prospective CTLD sequence with the group of structure-characterized CTLDs presented in
The implication is that also CTLDs, for which precise 3D structural information is not yet available, can nonetheless be used as frameworks in the construction of new classes of CTLD libraries. The specific additional steps involved in preparing starting materials for the construction of such a new class of CTLD library on the basis of a CTLD, for which no precise 3D structure is available, would be the following: (1) Alignment of the sequence of the new CTLD with the sequence shown in
W I G L R W - - - Q G KVKQCNS E W S D G S S V S - - Y E N W I E - - - - - - - -
W I G L T D Q - - N G P - - W R W V D G T D F E K G F K N W A P - - - - - - - -
W I G L H D P K K N R R - - W H W S S G S L V S - - Y K S W G I - - - - - - - -
W I G L T D E N Q E G E - - W Q W V D G T D T R S S F T F W K E - - - - - - - -
W I G L R N L D L K G E F I W V - - D G S H V D - - Y S N W A P - - - - - - - -
W I G L T D K D S E G T - - W K W V D G T P L T - - T A F W S T - - - - - - - -
W I G L T D Q G T E G N - - W R W V D G T P F DYVQS R R F W R K - - - - - - - -
W I G L S Y S E E H T A - - W L W E N G S A L S Q - Y L S F E T - - - - - - - -
W I G L N D R T I E G D F R W S - - D G H P M Q - - F E N W R P - - - - - - - -
W I G L H DPTQGTEPN G E G - W E W S S S D V M N - - Y F A W E R - - - - - - - -
W I G L N D R I V E Q D - - F Q W T D N T G L Q - - Y E N W R E - - - - - - - -
W I G I R K V N N V - - - - W V W - V G T Q K P L T EEAKN W A P - - - - - - - -
W I G V F R N S S H H P - - W V T M N G L A F K H E I K D S D N A - - - - - - -
W M G L S D L N Q E G T - - W Q W V D G S PLL P S - FKQ Y W N R - - - - - - - -
W I G L F R N V - E G T - - W L W I N N S P V S - - F V N W N T - - - - - - - -
W L G L N D M A A E G T - - - - W V D M T G A R I A Y K N W E T E I T - - - - -
W L G V H D R R A E G L - - Y L F E N G Q R V S - - F F A W HRSPRPELGAQPSASPHPLS
W L G A S D L N I E G R - - W L W - E G Q R R M N - Y T N W S P - - - - - - - -
W M G L H D - - Q N G P - - W K W V D G T D Y E T G F K N W R P - - - - - - - -
W M G L S N V W N Q C N - - W Q W S N A A M L R - - Y K A W A E - - - - - - - -
W V G L S Y D N K K K D - - W A W I D N R P S K L A L N T R K Y - - - - - - - -
W V G A D N - L Q D G A Y N F N W N D G V S L P T D S D L W S P - - - - - - - -
Y L G M I E D Q T P G D - - F H Y L D G A S V N - - Y T N W Y P - - - - - - - -
Y L S M N D I S T E G R - - F T Y P T G E I L V - - Y S N W A D - - - - - - - -
Y L S M N D I S K E G K - - F T Y P T G G S L D - - Y S N W A P - - - - - - - -
F L G I T D E V T E G Q - - F M Y V T G G R L T - - Y S N W K K - - - - - - - -
F L S M T D S K T E G K - - F T Y P T G E S L V - - Y S N W A P - - - - - - - -
F I G V N D L E R E G Q - - Y M F T D N T P L Q N - Y S N W N E - - - - - - - -
F V G L S D P - - E G Q R H W Q W V D Q T P - - - - Y NESSTFWHP - - - - - - - -
Sequences taken from: Berglund and Petersen (1992) [TN, tetranectin]; Bertrand et al. (1996) [LIT, lithostatin]; Mann et al. (2000) [MGL, mouse macrophage galactose lectin, KUCR, Kupffer cell receptor, NEU, chicken neurocan, PLC, perlucin, H1-ASR, asialoglycoprotein receptor]; Mio et al. (1998) [CPCP, cartilage proteoglycan core protein, IGE-FCR, IgE Fc receptor, PAP, pancreatitis-associated protein, MMR, mouse macrophage receptor, NKG2, Natural Killer group, SCGF, stem cell growth factor]; Mizuno et al. (1997) [IX-A and B, factor IX/X binding protein, MBP, mannose binding protein]; Ohtani et al. (1999) [BCON, bovine conglutinin, BCL43, bovine CL43, CL-L1, collectin liver 1, SP-A, surfactant protein A, SP-D, surfactant protein D]; Poget et al. (1999) [ESL, e-selectin, TU14, tunicate c-type lectin]; Tormo et al. (1999) [CD94,CD94 NK receptor domain, LY49A, LY49A NK receptor domain]; Zhang et al. (2000) [CHL, chicken hepatic lectin, TCL-1, trout c-type lectin, GP120, HIV gp 120-binding c-type lectin, DCIR, dendritic cell immuno receptor]
Of the 29 β2-strands,
Therefore, it is concluded that the four-residue β2 consensus sequence (“β2cseq”) may be specified as follows:
Accordingly the P2 consensus sequence may be summarized as follows:
All 29 β3-strands analyzed are initiated with the CysII residue canonical for all known CTLD sequences, and of the 29 β3-strands,
Therefore, it is concluded that the four-residue β3 consensus sequence (“(33cseq”) may be specified as follows:
Accordingly the β3 consensus sequence may be summarized as follows:
It is observed from the known 3D-structures of CTLDs (
Of the 29 central three residue motifs located at positions −5, −4 and −3 relative to the canonical CysIII residue in the β4-strand:
It has now been found that each member of the family of CTLD domains represents an attractive opportunity for the construction of new protein libraries from which members with affinity for new ligand targets can be identified and isolated using screening or selection methods. Such libraries may be constructed by combining a CTLD framework structure in which the CTLD's loop-region is partially or completely replaced with one or more randomized polypeptide segments.
One such system, where the protein used as scaffold is tetranectin or the CTLD domain of tetranectin, is envisaged as a system of particular interest, not least because the stability of the trimeric complex of tetranectin protomers is very high (International Patent Application Publication No. WO 98/56906 A2).
Tetranectin is a trimeric glycoprotein [Holtet et al. (1997), Nielsen et al. (1997)], which has been isolated from human plasma and found to be present in the extracellular matrix in certain tissues. Tetranectin is known to bind calcium, complex polysaccharides, plasminogen, fibrinogen/fibrin, and apolipoprotein (a). The interaction with plasminogen and apolipoprotein (a) is mediated by the so-called kringle 4 protein domain therein. This interaction is known to be sensitive to calcium and to derivatives of the amino acid lysine [Graversen et al. (1998)].
A human tetranectin gene has been characterised, and both human and murine tetranectin cDNA clones have been isolated. Both the human and the murine mature protein comprise 181 amino acid residues (
The object of the invention is to provide a new practicable method for the generation of useful protein products endowed with binding sites able to bind substance of interest with high affinity and specificity.
The invention describes one way in which such new and useful protein products may advantageously be obtained by applying standard combinatorial protein chemistry methods, commonly used in the recombinant antibody field, to generate randomized combinatorial libraries of protein modules, in which each member contains an essentially common core structure similar to that of a CTLD.
The variation of binding site configuration among naturally occurring CTLDs shows that their common core structure can accommodate many essentially different configurations of the ligand binding site. CTLDs are therefore particularly well suited to serve as a basis for constructing such new and useful protein products with desired binding properties.
In terms of practical application, the new artificial CTLD protein products can be employed in applications in which antibody products are presently used as key reagents in technical biochemical assay systems or medical in vitro or in vivo diagnostic assay systems or as active components in therapeutic compositions.
In terms of use as components of in vitro assay systems, the artificial CTLD protein products are preferable to antibody derivatives as each binding site in the new protein product is harboured in a single structurally autonomous protein domain. CTLD domains are resistant to proteolysis, and neither stability nor access to the ligand-binding site is compromised by the attachment of other protein domains to the N- or C-terminus of the CTLD. Accordingly, the CTLD binding module may readily be utilized as a building block for the construction of modular molecular assemblies, e.g. harbouring multiple CLTDs of identical or nonidentical specificity in addition to appropriate reporter modules like peroxidases, phosphatases or any other signal-mediating moiety.
In terms of in vivo use as essential component of compositions to be used for in vivo diagnostic or therapeutic purposes, artificial CTLD protein products constructed on the basis of human CTLDs are virtually identical to the corresponding natural CTLD protein already present in the body, and are therefore expected to elicit minimal immunological response in the patient. Single CTLDs are about half the mass of the smallest functional antibody derivative, the single-chain Fv derivative, and this small size may in some applications be advantageous as it may provide better tissue penetration and distribution, as well as a shorter half-life in circulation. Multivalent formats of CTLD proteins, e.g. corresponding to the complete tetranectin trimer or the further multimerized collectins, like e.g. mannose binding protein, provide increased binding capacity and avidity and longer circulation half-life.
One particular advantage of the preferred embodiment of the invention, arises from the fact that mammalian tetranectins, as exemplified by murine and human tetranectin, are of essentially identical structure. This conservation among species is of great practical importance as it allows straightforward swapping of polypeptide segments defining ligand-binding specificity between e.g. murine and human tetranectin derivatives. The option of facile swapping of species genetic background between tetranectin derivatives is in marked contrast to the well-known complications of effecting the “humanisation” of murine antibody derivatives.
Further advantages of the invention are:
The availability of a general and simple procedure for reliable conversion of an initially selected protein derivative into a final protein product, which without further reformatting may be produced in bacteria (e.g. Escherichia coli) both in small and in large scale (International Patent Application Publication No. WO 94/18227 A2).
The option of including several identical or non-identical binding sites in the same functional protein unit by simple and general means, thereby enabling the exploitation even of weak affinities by means of avidity in the interaction, or the construction of bi- or heterofunctional molecular assemblies (International Patent Application Publication No. WO 98/56906 A2).
The possibility of modulating binding by addition or removal of divalent metal ions (e.g. calcium ions) in combinational libraries with one or more preserved metal binding site(s) in the CTLDs.
The present invention provides a great number of novel and useful proteins each being a protein having the scaffold structure of C-type lectin-like domains (CTLD), said protein comprising a variant of a model CTLD wherein the α-helices and β-strands and connecting segments are conserved to such a degree that the scaffold structure of the CTLD is substantially maintained, while the loop region is altered by amino acid substitution, deletion, insertion or any combination thereof, with the proviso that said protein is not any of the known CTLD loop derivatives of C-type lectin-like proteins or C-type lectins listed in the following Table 2.
W L G L N A M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A A G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y A N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E A
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
W L G L N D M A A E G T W V D M T G A R I A Y K N W E T E I
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I R K V N N V F M Y V T G G R L T Y S N W K K D E P N
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W A P G E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W A D N E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K K D Q
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W R P G Q
F L G I T D Q N G Q F M Y V T G G R L T Y S N W K K D Q P D
F L G I T D Q N G P F M Y V T G G R L T Y S N W K K D Q P D
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K E G E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K E G E
F L G I T D E V T E G Q F M Y V T G G R L T Y S N W K E G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G Q
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G A
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V S Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G Q
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G A
Y L G M I E D Q T P G D F H Y L D G A S V N Y T N W Y P G E
Y L G M I E D Q T E G K F T Y P T G E A L V Y S N W A P G E
Y L G M I E D Q T E G Q F M Y V T G G R L T Y S N W K K D E
Y V G L T E G P S P G D F R Y S D G T P V N Y T N W Y R G E
Y V G L T E G P S P G D F R Y S D G T P V N Y T N W Y R G E
Y V G L T E G P T E G Q F M Y V T G G R L T Y S N W K K D E
F L S M T D V G T E G K F T Y P T G E A L V Y S N W A P G Q
W I G I R K V N N V W V W V G T Q A P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A A N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W K P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W K K G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W K K G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W A P G
W I G I R K V N N V W V W V G T Q K P L T E E A K N W K P G
W I G I R K N N K T W T W V G T K K A L T N E A E N W K D N
W I G I R K N N K T W T W V G T K K A L T N E A E N W K D N
WIGL T D Q N G P W R W V D G T D Y E K G F T H W R P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P G Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W R P G Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W A P K Q P
WIGL T D Q N G P W R W V D G T D Y E K G F T H W R P G Q P
WIGL T D Q N G P W K W V D G T D Y E T G F K N W R P G Q P
W I G L T D E N Q E G E W Q W V D G T D T R S S F T F W K E
W I G L T D E N Q E G E W Q W V D G T D T R S S F T F W K E
W I G L T D E N Q E G E W Q W V D G T D T R S S F T F W K E
W I G L T D E N Q E G E W Q W V D G T D T R S S F T F W K E
C A V L S G A A N G A W F D K R C
C A V L S G A A N G K W F D A R C
C A V L S G A A N G K W F D K A C
C A V L S G A A N G K W L D K R C
C A V L S G A A N G K W F A K R C
C A V L S G A A N G K W F E K R C
C A V L S G A A N G K W F N K R C
C V T I V D N G L W N D V S C
C V T I V D N G L W N D L S C
C V T I V D N G L W N D A S C
C V T I V D N G L W N D E S C
C V T I V Y I K R E K D N G L W N D I S C
C V T I V Y I K S P S D N G L W N D I S C
C V T I V D N G L W N D V Y C
C A H V W T S G Q W N D V Y C
C V E I F I K R E K D V G M W N D E R C
C V E I R I K R E K D V G M W N D E R C
C V E I D I K R E K D V G M W N D E R C
C V E I A I K R E K D V G M W N D E R C
C V E I S I K R E K D V G M W N D E R C
C V E I Y I K R E K D V G M W N D D R C
C V E I Y I K R E K D V G M W N D A R C
C V E I Y I K R E K D V G M W N D N R C
C V E I Y I K R E K D V G M W N D K R C
C V E I Y I K R E K D V G M W N D Q R C
C V E I Y I K D E K D V G M W N D E R C
C V E I Y I K S E K D V G M W N D E R C
C V E I Y I K E E K D V G M W N D E R C
C V E I Y I Q S P S A P G M W N D E H C
C V E I Y I R S P S A P G M W N D E H C
C V E I Y I E S P S A P G M W N D E H C
C V E I Y I K A P S A P G M W N D E H C
C V E I Y I K D P S A P G M W N D E H C
C V E I Y I K R P S A P G M W N D E H C
C V E I Y I K R E K A P G M W N D E H C
C V E I Y I K S P D A P G M W N D E H C
C A H V W T S G Q W N D A Y C
C A H V W T S G Q W N D V A C
Normally the model CTLD is defined by having a 3D structure that conforms to the secondary-structure arrangement illustrated in
However, also a CTLD, for which no precise 3D structure is available, can be used as a model CTLD, such CTLD being defined by showing sequence similarity to a previously recognised member of the CTLD family as expressed by an amino acid sequence identity of at least 22%, preferably at least 25% and more preferably at least 30%, and by containing the cysteine residues necessary for establishing the conserved two-disulfide bridge topology (i.e. CysI, CysII, CysIII and CysIV). The loop region, consisting of the loop segments LSA and LSB, and its flanking β-strand structural elements can then be identified by inspection of the sequence alignment with the collection of CTLDs shown in
The same considerations apply for determining whether in a model CTLD the α-helices and β-strands and connecting segments are conserved to such a degree that the scaffold structure of the CTLD is substantially maintained.
It may be desirable that up to 10, preferably up to 4, and more preferably 1 or 2, amino acid residues are substituted, deleted or inserted in the α-helices and/or β-strands and/or connecting segments of the model CTLD. In particular, changes of up to 4 residues may be made in the β-strands of the model CTLD as a consequence of the introduction of recognition sites for one or more restriction endonucleases in the nucleotide sequence encoding the CTLD to facilitate the excision of part or all of the loop region and the insertion of an altered amino acid sequence instead while the scaffold structure of the CTLD is substantially maintained.
Of particular interest are proteins wherein the model CTLD is that of a tetranectin. Well known tetranectins the CTLDs of which can be used as model CTLDs are human tetranectin and murine tetranectin. The proteins according to the invention thus comprise variants of such model CTLDs.
The proteins according to the invention may comprise N-terminal and/or C-terminal extensions of the CTLD variant, and such extensions may for example contain effector, enzyme, further binding and/or multimerising functions. In particular, said extension may be the non-CTLD-portions of a native C-type lectin-like protein or C-type lectin or a “soluble” variant thereof lacking a functional transmembrane domain.
The proteins according to the invention may also be multimers of a moiety comprising the CTLD variant, e.g. derivatives of the native tetranectin trimer.
In a preferred aspect the present invention provides a combinatorial library of proteins having the scaffold structure of C-type lectin-like domains (CTLD), said proteins comprising variants of a model CTLD wherein the α-helices and β-strands are conserved to such a degree that the scaffold structure of the CTLD is substantially maintained, while the loop region or parts of the loop region of the CTLD is randomized with respect to amino acid sequence and/or number of amino acid residues.
The proteins making up such a library comprise variants of model CTLDs defined as for the above proteins according to the invention, and the variants may include the changes stated for those proteins.
In particular, the combinatorial library according to the invention may consist of proteins wherein the model CTLD is that of a tetranectin, e.g. that of human tetranectin or that of murine tetranectin.
The combinatorial library according to the invention may consist of proteins comprising N-terminal and/or C-terminal extensions of the CTLD variant, and such extensions may for example contain effector, enzyme, further binding and/or multimerising functions. In particular, said extensions may be the non-CTLD-portions of a native C-type lectin-like protein or C-type lectin or a “soluble” variant thereof lacking a functional transmembrane domain.
The combinatorial library according to the invention may also consist of proteins that are multimers of a moiety comprising the CTLD variant, e.g. derivatives of the native tetranectin trimer.
The present invention also provides derivatives of a native tetranectin wherein up to 10, preferably up to 4, and more preferably 1 or 2, amino acid residues are substituted, deleted or inserted in the α-helices and/or β-strands and/or connecting segments of its CTLD as well as nucleic acids encoding such derivatives. Specific derivatives appear from SEQ ID Nos: 02, 04, 09, 11, 13, 15, 29, 31, 36, and 38; and nucleic acids comprising nucleotide inserts encoding specific tetranectin derivatives appear from SEQ ID Nos: 12, 14, 35, and 37.
The invention comprises a method of constructing a tetranectin derivative adapted for the preparation of a combinatorial library according to the invention, wherein the nucleic acid encoding the tetranectin derivative has been modified to generate endonuclease restriction sites within nucleic acid segments encoding β2, β3 or β4, or up to 30 nucleotides upstream or downstream in the sequence from any nucleotide which belongs to a nucleic acid segment encoding β2, β3 or β4.
The invention also comprises the use of a nucleotide sequence encoding a tetranectin, or a derivative thereof wherein the scaffold structure of its CTLD is substantially maintained, for preparing a library of nucleotide sequences encoding related proteins by randomising part or all of the nucleic acid sequence encoding the loop region of its CTLD.
Further, the present invention provides nucleic acid comprising any nucleotide sequence encoding a protein according to the invention.
In particular, the invention provides a library of nucleic acids encoding proteins of a combinatorial library according to the invention, in which the members of the ensemble of nucleic acids, that collectively constitute said library of nucleic acids, are able to be expressed in a display system, which provides for a logical, physical or chemical link between entities displaying phenotypes representing properties of the displayed expression products and their corresponding genotypes.
In such a library the display system may be selected from
A well-known and useful display system is the “Recombinant Phage Antibody System” with the phagemid vector “pCANTAB 5E” supplied by Amersham Pharmacia Biotech (code no. 27-9401-01).
Further, the present invention provides a method of preparing a protein according to the invention, wherein the protein comprises at least one or more, identical or not identical, CTLD domains with novel loop-region sequences which has (have) been isolated from one or more CTLD libraries by screening or selection. At least one such CTLD domain may have been further modified by mutagenesis; and the protein containing at least one CTLD domain may have been assembled from two or more components by chemical or enzymatic coupling or crosslinking.
Also, the present invention provides a method of preparing a combinatorial library according to the invention comprising the following steps:
In a further aspect, the present invention provides a method of screening a combinatorial library according to the invention for binding to a specific target which comprises the following steps:
In a still further aspect, the present invention provides a method of reformatting a protein according to the invention or selected from a combinatorial library according to the invention and containing a CTLD variant exhibiting desired binding properties, in a desired alternative species-compatible framework by excising the nucleic acid fragment encoding the loop region-substituting polypeptide and any required single framework mutations from the nucleic acid encoding said protein using PCR technology, site directed mutagenesis or restriction enzyme digestion and inserting said nucleic acid fragment into the appropriate location(s) in a display—or protein expression vector that harbours a nucleic acid sequence encoding the desired alternative CTLD framework.
The four cysteine residues involved in the formation of the two conserved disulfide bridges of CTLDs are indicated and enumerated in the Figure as “CI”, “CII”, “CIII” and “CIV”, respectively. The two conserved disulfide bridges are CI-CIV and CII-CIII, respectively.
The ten C-type lectins are
“α” denotes an α-helix; “β” denotes a β-strand; and “L” denotes a loop.
htlec: the sequence derived from hTN; mtlec: the sequence derived from mTN. The position of the restriction endonuclease sites for Bgl II, Kpn I, and Mun I are indicated.
FX-mtlec part of the H6FX-mtlec fusion protein produced by pT7H6FX-mtlec.
I. Definitions
The terms “C-type lectin-like protein” and “C-type lectin” are used to refer to any protein present in, or encoded in the genomes of, any eukaryotic species, which protein contains one or more CTLDs or one or more domains belonging to a subgroup of CTLDs, the CRDs, which bind carbohydrate ligands. The definition specifically includes membrane attached C-type lectin-like proteins and C-type lectins, “soluble” C-type lectin-like proteins and C-type lectins lacking a functional transmembrane domain and variant C-type lectin-like proteins and C-type lectins in which one or more amino acid residues have been altered in vivo by glycosylation or any other post-synthetic modification, as well as any product that is obtained by chemical modification of C-type lectin-like proteins and C-type lectins.
In the claims and throughout the specification certain alterations may be defined with reference to amino acid residue numbers of a CTLD domain or a CTLD-containing protein. The amino acid numbering starts at the first N-terminal amino acid of the CTLD or the native or artificial CTLD-containing protein product, as the case may be, which shall in each case be indicated by unambiguous external literature reference or internal reference to a figure contained herein within the textual context.
The terms “amino acid”, “amino acids” and “amino acid residues” refer to all naturally occurring L-α-amino acids. This definition is meant to include norleucine, ornithine, and homocysteine. The amino acids are identified by either the single-letter or three-letter designations:
The naturally occurring L-α-amino acids may be classified according to the chemical composition and properties of their side chains. They are broadly classified into two groups, charged and uncharged. Each of these groups is divided into subgroups to classify the amino acids more accurately:
The terms “amino acid alteration” and “alteration” refer to amino acid substitutions, deletions or insertions or any combinations thereof in a CTLD amino acid sequence. In the CTLD variants of the present invention such alteration is at a site or sites of a CTLD amino acid sequence. Substitutional variants herein are those that have at least one amino acid residue in a native CTLD sequence removed and a different amino acid inserted in its place at the same position. The substitutions may be single, where only one amino acid in the molecule has been substituted, or they may be multiple, where two or more amino acids have been substituted in the same molecule.
The designation of the substitution variants herein consists of a letter followed by a number followed by a letter. The first (leftmost) letter designates the amino acid in the native (unaltered) CTLD or CTLD-containing protein. The number refers to the amino acid position where the amino acid substitution is being made, and the second (righthand) letter designates the amino acid that is used to replace the native amino acid. As mentioned above, the numbering starts with “1” designating the N-terminal amino acid sequence of the CTLD or the CTLD-containing protein, as the case may be. Multiple alterations are separated by a comma (,) in the notation for ease of reading them.
The terms “nucleic acid molecule encoding”, “DNA sequence encoding”, and “DNA encoding” refer to the order or sequence of deoxyribonucleotides along a strand of deoxyribonucleic acid. The order of these deoxyribonucleotides determines the order of amino acids along the polypeptide chain. The DNA sequence thus encodes the amino acid sequence.
The terms “mutationally randomized sequence”, “randomized polypeptide segment”, “randomized amino acid sequence”, “randomized oligonucleotide” and “mutationally randomized sequence”, as well as any similar terms used in any context to refer to randomized sequences, polypeptides or nucleic acids, refer to ensembles of polypeptide or nucleic acid sequences or segments, in which the amino acid residue or nucleotide at one or more sequence positions may differ between different members of the ensemble of polypeptides or nucleic acids, such that the amino acid residue or nucleotide occurring at each such sequence position may belong to a set of amino acid residues or nucleotides that may include all possible amino acid residues or nucleotides or any restricted subset thereof. Said terms are often used to refer to ensembles in which the number of amino acid residues or nucleotides is the same for each member of the ensemble, but may also be used to refer to such ensembles in which the number of amino acid residues or nucleotides in each member of the ensemble may be any integer number within an appropriate range of integer numbers.
II. Construction and Utility of Combinatorial CTLD Libraries
Several systems displaying phenotype, in terms of putative ligand binding modules or modules with putative enzymatic activity, have been described. These include: phage display (e.g. the filamentous phage fd [Dunn (1996), Griffiths amd Duncan (1998), Marks et al. (1992)], phage lambda [Mikawa et al. (1996)]), display on eukarotic virus (e.g. baculovirus [Ernst et al. (2000)]), cell display (e.g. display on bacterial cells [Benhar et al. (2000)], yeast cells [Boder and Wittrup (1997)], and mammalian cells [Whitehorn et al. (1995)], ribosome linked display [Schaffitzel et al. (1999)], and plasmid linked display [Gates et al. (1996)].
The most commonly used method for phenotype display and linking this to genotype is by phage display. This is accomplished by insertion of the reading frame encoding the scaffold protein or protein of interest into an intra-domain segment of a surface exposed phage protein. The filamentous phage fd (e.g. M13) has proven most useful for this purpose. Polypeptides, protein domains, or proteins are the most frequently inserted either between the “export” signal and domain 1 of the fd gene III protein or into a so-called hinge region between domain 2 and domain 3 of the fd-phage gene III protein. Human antibodies are the most frequently used proteins for the isolation of new binding units, but other proteins and domains have also been used (e.g. human growth hormone [Bass et al. (1990)], alkaline phosphatase [McCafferty et al. (1991)], β-lactamase inhibitory protein [Huang et al. (2000)], and cytotoxic T lymphocyte-associated antigen 4 [Hufton et al. (2000)]. The antibodies are often expressed and presented as scFv or Fab fusion proteins. Three strategies have been employed. Either a specific antibody is used as a scaffold for generating a library of mutationally randomized sequences within the antigen binding clefts [e.g. Fuji et al. (1998)] or libraries representing large ensembles of human antibody encoding genes from non-immunised hosts [e.g. Nissim et al. (1994)] or from immunised hosts [e.g. Cyr and Hudspeth (2000)] are cloned into the fd phage vector.
The general procedure for accomplishing the generation of a display system for the generation of CTLD libraries comprise essentially
Nucleic acid fragments may be inserted in specific locations into receiving nucleic acids by any common method of molecular cloning of nucleic acids, such as by appropriately designed PCR manipulations in which chemically synthesized nucleic acids are copy-edited into the receiving nucleic acid, in which case no endonuclease restriction sites are required for insertion. Alternatively, the insertion/excision of nucleic acid fragments may be facilitated by engineering appropriate combinations of endonuclease restriction sites into the target nucleic acid into which suitably designed oligonucleotide fragments may be inserted using standard methods of molecular cloning of nucleic acids.
It will be apparent that interesting CTLD variants isolated from CTLD libraries in which restriction endonuclease sites have been inserted for convenience may contain mutated or additional amino acid residues that neither correspond to residues present in the original CTLD nor are important for maintaining the interesting new affinity of the CTLD variant. If desirable, e.g. in case the product needs to be rendered as non-immunogenic as possible, such residues may be altered or removed by back-mutation or deletion in the specific clone, as appropriate.
The ensemble consisting of a multitude of nucleic acid fragments may be obtained by ordinary methods for chemical synthesis of nucleic acids by directing the step-wise synthesis to add pre-defined combinations of pure nucleotide monomers or a mixture of any combination of nucleotide monomers at each step in the chemical synthesis of the nucleic acid fragment. In this way it is possible to generate any level of sequence degeneracy, from one unique nucleic acid sequence to the most complex mixture, which will represent a complete or incomplete representation of maximum number unique sequences of 4N, where N is the number of nucleotides in the sequence.
Complex ensembles consisting of multitudes of nucleic acid fragments may, alternatively, be prepared by generating mixtures of nucleic acid fragments by chemical, physical or enzymatic fragmentation of high-molecular mass nucleic acid compositions like, e.g., genomic nucleic acids extracted from any organism. To render such mixtures of nucleic acid fragments useful in the generation of molecular ensembles, as described here, the crude mixtures of fragments, obtained in the initial cleavage step, would typically be size-fractionated to obtain fragments of an approximate molecular mass range which would then typically be adjoined to a suitable pair of linker nucleic acids, designed to facilitate insertion of the linker-embedded mixtures of size-restricted oligonucleotide fragments into the receiving nucleic acid vector.
To facilitate the construction of combinatorial CTLD libraries in tetranectin, the model CTLD of the preferred embodiment of the invention, suitable restriction sites located in the vicinity of the nucleic acid sequences encoding β2, β3 and β4 in both human and murine tetranectin were designed with minimal perturbation of the polypeptide sequence encoded by the altered sequences. It was found possible to establish a design strategy, as detailed below, by which identical endonuclease restriction sites could be introduced at corresponding locations in the two sequences, allowing interesting loop-region variants to be readily excised from a recombinant murine CTLD and inserted correctly into the CTLD framework of human tetranectin or vice versa.
Analysis of the nucleotide sequence encoding the mature form of human tetranectin reveals (
Mutation, by site directed mutagenesis, of G513 to A and of C514 to T in the nucleotide sequence encoding human tetranectin would introduce a Mun I restriction endonuclease recognition site therein, located at position 511 to 516, and mutation of G513 to A in the nucleotide sequence encoding murine tetranectin would introduce a Mun I restriction endonuclease site therein at a position corresponding to the Mun I site in human tetranectin, without affecting the amino acid sequence of either of the encoded protomers. Mutation, by site directed mutagenesis, of C327 to G and of G386 to C in the nucleotide sequence encoding murine tetranectin would introduce a Bgl II and a Kas I restriction endonuclease recognition site, respectively, therein. Additionally, A325 in the nucleotide sequence encoding murine tetranectin is mutagenized to a G. These three mutations would affect the encoded amino acid sequence by substitution of Asn109 to Glu and Gly129 to Ala, respectively. Now, the restriction endonuclease Kas I is known to exhibit marked site preference and cleaves only slowly the tetranectin coding region. Therefore, a recognition site for another restriction endonuclease substituting the Kas I site is preferred (e.g. the recognition site for the restriction endonuclease Kpn I, recognition sequence GGTACC). The nucleotide and amino acid sequences of the resulting tetranectin derivatives, human tetranectin lectin (htlec) and murine tetranectin lectin (mtlec) are shown in
The presence of a common set of recognition sites for the restriction endonucleases Bgl II, Kas I or Kpn I, and Mun I in the ensemble of tetranectin and CTLD derivatives allows for the generation of protein libraries with randomized amino acid sequence in one or more of the loops and at single residue positions in β4 comprising the lectin ligand binding region by ligation of randomized oligonucleotides into properly restricted phagemid vectors encoding htlec, mtlec, htCTLD, or mtCTLD derivatives.
After rounds of selection on specific targets (e.g. eukaryotic cells, virus, bacteria, specific proteins, polysaccharides, other polymers, organic compounds etc.) DNA may be isolated from the specific phages, and the nucleotide sequence of the segments encoding the ligand-binding region determined, excised from the phagemid DNA and transferred to the appropriate derivative expression vector for heterologous production of the desired product. Heterologous production in a prokaryote may be preferred because an efficient protocol for the isolation and refolding of tetranectin and derivatives has been reported (International Patent Application Publication WO 94/18227 A2).
A particular advantage gained by implementing the technology of the invention, using tetranectin as the scaffold structure, is that the structures of the murine and human tetranectin scaffolds are almost identical, allowing loop regions to be swapped freely between murine and human tetranectin derivatives with retention of functionality. Swapping of loop regions between the murine and the human framework is readily accomplished within the described system of tetranectin derivative vectors, and it is anticipated, that the system can be extended to include other species (e.g. rat, old and new world monkeys, dog, cattle, sheep, goat etc.) of relevance in medicine or veterinary medicine in view of the high level of homology between man and mouse sequences, even at the genetic level. Extension of this strategy to include more species may be rendered possible as and when tetranectin is eventually cloned and/or sequenced from such species.
Because the C-type lectin ligand-binding region represents a different topological unit compared to the antigen binding clefts of the antibodies, we envisage that the selected binding specificities will be of a different nature compared to the antibodies. Further, we envisage that the tetranectin derivatives may have advantages compared to antibodies with respect to specificity in binding sugar moieties or polysaccharides. The tetranectin derivatives may also be advantageous in selecting binding specificities against certain natural or synthetic organic compounds.
Several CTLDs are known to bind calcium ions, and binding of other ligands is often either dependent on calcium (e.g. the collectin family of C-type lectins, where the calcium ion bound in site 2 is directly involved in binding the sugar ligand [Weis and Drickamer (1996)]) or sensitive to calcium (e.g. tetranectin, where binding of calcium involves more of the side chains known otherwise to be involved in plasminogen kringle 4 binding [Graversen et al. (1998)]). The calcium binding sites characteristic of the C-type lectin-like protein family are comprised by residues located in loop 1, loop 4 and β-strand 4 and are dependent on the presence of a proline residue (often interspacing loop 3 and loop 4 in the structure), which upon binding is found invariantly in the cis conformation. Moreover, binding of calcium is known to enforce structural changes in the CTLD loop-region [Ng et al. (1998a,b)]. We therefore envisage, that binding to a specific target ligand by members of combinational libraries with preserved CTLD metal binding sites may be modulated by addition or removal of divalent metal ions (e.g. calcium ions) either because the metal ion may be directly involved in binding, because it is a competitive ligand, or because binding of the metal ion enforces structural rearrangements within the putative binding site.
The trimeric nature of several members of the C-type lectin and C-type lectin-like protein family, including tetranectin, and the accompanying avidity in binding may also be exploited in the creation of binding units with very high binding affinity.
As can be appreciated from the disclosure above, the present invention has a broad general scope and a wide area of application. Accordingly, the following examples, describing various embodiments thereof, are offered by way of illustration only, not by way of limitation.
Construction of Tetranectin Derived E. coli Expression Plasmids and Phagemids
The expression plasmid pT7H6FX-htlec, encoding the FX-htlec (SEQ ID NO:01) part of full length H6FX-htlec fusion protein, was constructed by a series of four consecutive site-directed mutagenesis experiments starting from the expression plasmid pT7H6-rTN 123 [Holtet et al. (1997)] using the QuickChange™ Site-Directed Mutagenesis Kit (Stratagene, La Jolla, Calif.) and performed as described by the manufacturer. Mismatching primer pairs introducing the desired mutations were supplied by DNA Technology (Aarhus, Denmark). An outline of the resulting pT7H6FX-htlec expression plasmid is shown in
The expression plasmid pT7H6FX-htCTLD, encoding the FX-htCTLD (SEQ ID NO: 03) part of the H6FX-htCTLD fusion protein, was constructed by amplification and subcloning into the plasmid pT7H6 (i.e. amplification in a polymerase chain reaction using the expression plasmid pT7H6-htlec as template, and otherwise the primers, conditions, and subcloning procedure described for the construction of the expression plasmid pT7H6TN3 [Holtet et al. (1997)]. An outline of the resulting pT7H6FX-htCTLD expression plasmid is shown in
The phagemids, pPhTN and pPhTN3, were constructed by ligation of the Sfi I and Not I restricted DNA fragments amplified from the expression plasmids pT7H6-rTN 123 (with the oligonucleotide primers 5-CGGCTGAGCGGCCCAGCCGGCCATGGCCGAGCCACCAACCCAGAAGC-3′ [SEQ ID NO:05] and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:06]) and pT7H6FX-htCTLD (with the oligonucleotide primers 5′-CGGCTGAGCGGCCCAGCCGGCCATGGCCGCCCTGCAGACGGTC-3′ [SEQ ID NO:07] and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:06]), respectively, into a Sfi I and Not I precut vector, pCANTAB 5E supplied by Amersham Pharmacia Biotech (code no. 27-9401-01) using standard procedures. Outlines of the resulting pPhTN and pPhTN3 phagemids are shown in
The phagemids, pPhtlec and pPhtCTLD, were constructed by ligation of the Sfi I and Not I restricted DNA fragments amplified from the expression plasmids pT7H6FX-htlec (with the oligonucleotide primers 5-CGGCTGAGCGGCCCAGCCGGCCATGGCCGAGCCACCAACCCAGAAGC-3′ [SEQ ID NO:05] and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:06]) and pT7H6FX-htCTLD (with the oligonucleotide primers 5′-CGGCTGAGCGGCCCAGCCGGCCATGGCCGCCCTGCAGACGGTC-3′ [SEQ ID NO:07] and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:06]), respectively, into a Sfi I and Not I precut vector, pCANTAB 5E supplied by Amersham Pharmacia Biotech (code no. 27-9401-01) using standard procedures. Outlines of the resulting pPhtlec and pPhtCTLD phagemids are shown in
A plasmid clone, pUC-mtlec, containing the nucleotide sequence corresponding to the murine tetranectin derivative mtlec (
The expression plasmids pT7H6FX-mtlec and pT7H6FX-mtCTLD may be constructed by ligation of the Bam HI and Hind III restricted DNA fragments, amplified from the pUC-mtlec plasmid with the oligonucleotide primer pair 5-CTGGGATCCATCCAGGGTCGCGAGTCACCCACTCCCAAGG-3′ (SEQ ID NO:25) and 5′-CCGAAGCTTACACAATGGCAAACTGGC-3′ (SEQ ID NO:26), and with the oligonucleotide primer pair 5′-CTGGGATCCATCCAGGGTCGCGCCTTACAGACTGTGGTC-3′ (SEQ ID NO:27), and 5′-CCGAAGCTTACACAATGGCAAACTGGC-3′ (SEQ ID NO:26), respectively, into Bam HI and Hind III precut pT7H6 vector using standard procedures. An outline of the expression plasmids pT7H6FX-mtlec and pT7H6FX-mtCTLD is shown in
The phagemids pPmtlec and pPmtCTLD may be constructed by ligation of the Sfi I and Not I restricted DNA fragments (amplified from the pUC-mtlec plasmid with the oligonucleotide primer pair 5-CGGCTGAGCGGCCCAGCCGGCCATGGCCGAGTCACCCACTCCCAAGG-3′ [SEQ ID NO:32], and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:33] and with the oligonucleotide primers 5′-CGGCTGAGCGGCCCAGCCGGCCATGGCCGCCTTACAGACTGTGGTC-3′ [SEQ ID NO:34] and 5′-CCTGCGGCCGCCACGATCCCGAACTGG-3′ [SEQ ID NO:33], respectively) into a Sfi I and Not I precut vector pCANTAB 5E supplied by Amersham Pharmacia Biotech (code no. 27-9401-01) using standard procedures. Outlines of the pPmtlec and pPmtCTLD plasmids are shown in
Demonstration of Successful Display of Phtlec and PhTN3 on Phages.
In order to verify that the Phtlec and PhTN3 Gene III fusion proteins can indeed be displayed by the recombinant phage particles, the phagemids pPhtlec and pPhTN3 (described in Example 1) were transformed into E. coli TG1 cells and recombinant phages produced upon infection with the helper phage M13K07. Recombinant phages were isolated by precipitation with poly(ethylene glycol) (PEG 8000) and samples of Phtlec and PhTN3 phage preparations as well as a sample of helper phage were subjected to an ELISA-type sandwich assay, in which wells of a Maxisorb (Nunc) multiwell plate were first incubated with anti-human tetranectin or bovine serum albumin (BSA) and blocked in skimmed milk or skimmed milk/EDTA. Briefly, cultures of pPhtlec and pPhTN3 phagemid transformed TG1 cells were grown at 37° C. in 2xTY-medium supplemented with 20 glucose and 100 mg/L ampicillin until A600 reached 0.5. By then the helper phage, M13KO7, was added to a concentration of 5×109 pfu/mL. The cultures were incubated at 37° C. for another 30 min before cells were harvested by centrifugation and resuspended in the same culture volume of 2×TY medium supplemented with 50 mg/L kanamycin and 100 mg/L ampicillin and transferred to a fresh set of flasks and grown for 16 hours at 25° C. Cells were removed by centrifugation and the phages precipitated from 20 mL culture supernatant by the addition of 6 mL of ice cold 200 PEG 8000, 2.5 M NaCl. After mixing the solution was left on ice for one hour and centrifuged at 4° C. to isolate the precipitated phages. Each phage pellet was resuspended in 1 mL of 10 mM tris-HCl pH 8, 1 mM EDTA (TE) and incubated for 30 min before centrifugation. The phage containing supernatant was transferred to a fresh tube. Along with the preparation of phage samples, the wells of a Maxisorb plate was coated overnight with (70 μL) rabbit anti-human tetranectin (a polyclonal antibody from DAKO A/S, code no. A0371) in a 1:2000 dilution or with (70 μL) BSA (10 mg/mL). Upon coating, the wells were washed three times with PBS (2.68 mM KCl, 1.47 mM KH2PO4, 137 mM NaCl, 8.10 mM Na2HPO4, pH 7.4) and blocked for one hour at 37° C. with 280 μL of either 3% skimmed milk in PBS, or 3% skimmed milk, 5 mM EDTA in PBS. Anti-tetranectin coated and BSA coated wells were then incubated with human Phtlec-, PhTN3-, or helper phage samples for 1 hour and then washed 3 times in PBS buffer supplemented with the appropriate blocking agent. Phages in the wells were detected after incubation with HRP-conjugated anti-phage conjugate (Amersham Pharmacia, code no. 27-9421-01) followed by further washing. HRP activities were then measured in a 96-well ELISA reader using a standard HRP chromogenic substrate assay.
Phtlec and PhTN3 phages produced strong responses (14 times background) in the assay, irrespective of the presence or absence of EDTA in the blocking agent, whereas helper phage produced no response above background readings in either blocking agent. Only low binding to BSA was observed (
It can therefore be concluded that the human Phtlec and PhTN3 phages both display epitopes that are specifically recognized by the anti-human tetranectin antibody.
Demonstration of authentic ligand binding properties of Phtlec and PhTN3 displayed on phage
The apo-form of the CTLD domain of human tetranectin binds in a lysine-sensitive manner specifically to the kringle 4 domain of human plasminogen [Graversen et al. (1998)]. Binding of tetranectin to plasminogen can be inhibited by calcium which binds to two sites in the ligand-binding site in the CTLD domain (Kd approx. 0.2 millimolar) or by lysine-analogues like AMCHA (6-amino-cyclohexanoic acid), which bind specifically in the two stronger lysine-binding sites in plasminogen of which one is located in kringle 1 and one is located in kringle 4 (Kd approx. 15 micromolar).
To demonstrate specific AMCHA-sensitive binding of human Phtlec and PhTN3 phages to human plasminogen, an ELISA assay, in outline similar to that employed to demonstrate the presence of displayed Phlec and PhCTLD GIII fusion proteins on the phage particles (cf. Example 2), was devised.
Wells were coated with solutions of human plasminogen (10 μg/mL), with or without addition of 5 mM AMCHA. Control wells were coated with BSA. Two identical arrays were established, one was subjected to blocking of excess binding capacity with 3% skimmed milk, and one was blocked using 3% skimmed milk supplemented with 5 mM EDTA. Where appropriate, blocking, washing and phage stock solutions were supplemented by 5 mM AMCHA. The two arrays of wells were incubated with either Phtlec-, or PhTN3-, or helper phage samples, and after washing the amount of phage bound in each well was measured using the HRP-conjugated antiphage antibody as above. The results are shown in
In conclusion, the results show that the Phtlec and PhTN3 Gene III fusion proteins displayed on the phage particles exhibit plasminogen-binding properties corresponding to those of authentic tetranectin, and that the physical and biochemical properties of Phtlec and PhTN3 phages are compatible with their proposed use as vehicles for the generation of combinatorial libraries from which CTLD derived units with new binding properties can be selected.
Construction of the phage libraries Phtlec-lb001 and Phtlec-lb002.
All oligonucleotides used in this example were supplied by DNA Technology (Aarhus, Denmark).
The phage library Phtlec-lb001, containing random amino acid residues corresponding to Phtlec (SEQ ID NO: 12) positions 141-146 (loop 3), 150-153 (part of loop 4), and residue 168 (Phe in β4), was constructed by ligation of 20 μg KpnI and MunI restricted pPhtlec phagemid DNA (cf, Example 1) with 10 μg of KpnI and MunI restricted DNA fragment amplified from the oligonucleotide htlec-lib1-tp (SEQ ID NO: 39), where N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence and the oligonucleotides htlec-lib1-rev (SEQ ID NO: 40) and htlec-lib1/2-fo (SEQ ID NO: 41) as primers using standard conditions. The ligation mixture was used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells were plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated over night at 30° C.
The phage library Phtlec-lb002, containing random amino acid residues corresponding to Phtlec (SEQ ID NO: 12) positions 121-123, 125 and 126 (most of loop 1), and residues 150-153 (part of loop 4) was constructed by ligation of 20 μg BglII and MunI restricted pPhtlec phagemid DNA (cf, EXAMPLE 1) with 15 μg of BglII and MunI restricted DNA fragment amplified from the pair of oligonucleotides htlec-lib2-tprev (SEQ ID NO: 42) and htlec-lib2-tpfo (SEQ ID NO: 43), where N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence and the oligonucleotides htlec-lib2-rev (SEQ ID NO: 44) and htlec-lib1/2-fo (SEQ ID NO: 41) as primers using standard conditions. The ligation mixture was used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells were plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated overnight at 30° C.
The titer of the libraries Phtlec-lb001 and −lb002 was determined to 1.4*109 and 3.2*109 clones, respectively. Six clones from each library were grown and phagemid DNA isolated using a standard miniprep procedure, and the nucleotide sequence of the loop-region determined (DNA Technology, Aarhus, Denmark). One clone from each library failed, for technical reasons, to give reliable nucleotide sequence, and one clone from Phtlec-lib001 apparently contained a major deletion. The variation of nucleotide sequences, compared to Phtlec (SEQ ID NO: 12), of the loop-regions of the other nine clones (lb001-1, lb001-2, lb001-3, lb001-4, lb002-1, lb002-2, lb002-3, lb002-4, and lb002-5) is shown in Table 3.
Construction of the Phage Library PhtCTLD-lb003
All oligonucleotides used in this example were supplied by DNA Technology (Aarhus, Denmark).
The phage library PhtCTLD-lb003, containing random amino acid residues corresponding to PhtCTLD (SEQ ID NO: 15) positions 77 to 79 and 81 to 82 (loop 1) and 108 to 109 (loop 4) was constructed by ligation of 20 μg BglII and MunI restricted pPhtCTLD phagemid DNA (cf. Example 1) with 10 g of a BglII and MunI restricted DNA fragment population encoding the appropriately randomized loop 1 and 4 regions with or without two and three random residue insertions in loop 1 and with three and four random residue insertions in loop 4. The DNA fragment population was amplified, from six so-called assembly reactions combining each of the three loop 1 DNA fragments with each of the two loop 4 DNA fragments as templates and the oligonucleotides TN-lib3-rev (SEQ ID NO: 45) and loop 3-4-5 tagfo (SEQ ID NO: 46) as primers using standard procedures. Each of the three loop 1 fragments was amplified in a reaction with either the oligonucleotides loop1b (SEQ ID NO: 47), loop1c (SEQ ID NO: 48), or loop1d (SEQ ID NO: 49) as template and the oligonucleotides TN-lib3-rev (SEQ ID NO: 45) and TN-KpnI-fo (SEQ ID NO: 50) as primers, and each of the two DNA loop 4 fragments was amplified in a reaction with either the oligonucleotide loop4b (SEQ ID NO: 51) or loop4c (SEQ ID NO: 52) as template and the oligonucleotides loop3-4rev (SEQ ID NO: 53) and loop3-4fo (SEQ ID NO: 54) as primers using standard procedures. In the oligonucleotide sequences N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence. The ligation mixture was used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells were plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated over night at 30° C.
The size of the resulting library, PhtCTLD-lb003, was determined to 1.4*1010 clones. Twenty four clones from the library were grown and phages and phagemid DNA isolated. The nucleotide sequences of the loop-regions were determined (DNA Technology, Aarhus, Denmark) and binding to a polyclonal antibody against tetranectin, anti-TN (DAKO A/S, Denmark), analyzed in an ELISA-type assay using HRP conjugated anti-gene VIII (Amersham Pharmacia Biotech) as secondary antibody using standard procedures. Eighteen clones were found to contain correct loop inserts, one clone contained the wild type loop region sequence, one a major deletion, two contained two or more sequences, and two clones contained a frameshift mutation in the region. Thirteen of the 18 clones with correct loop inserts, the wild type clone, and one of the mixed isolates reacted strongly with the polyclonal anti-TN antibody. Three of the 18 correct clones reacted weakly with the antibody, whereas, two of the correct clones, the deletion mutant, one of the mixed, and the two frameshift mutants did not show a signal above background.
Phage Selection by Biopanning on Anti-TN Antibody.
Approximately 1011 phages from the PhtCTLD-lb003 library was used for selection in two rounds on the polyclonal anti-TN antibody by panning in Maxisorb immunotubes (NUNC, Denmark) using standard procedures. Fifteen clones out of 7*107 from the plating after the second selection round were grown and phagemid DNA isolated and the nucleotide sequence determined. All 15 clones were found to encode correct and different loop sequences.
Model Selection of CTLD-Phages on Plasminogen.
In order to demonstrate that tetranectin derived CTLD bearing phages can be selected from a population of phages, mixtures of PhtCTLD phages isolated from a E. coli TG1 culture transformed with the phagemid pPhtCTLD (cf, EXAMPLE 1) after infection with M13K07 helper phage and phages isolated from a culture transformed with the phagemid pPhtCPB after infection with M13K07 helper phage at ratios of 1:10 and 1:105, respectively were used in a selection experiment using panning in 96-well Maxisorb micro-titerplates (NUNC, Denmark) and with human plasminogen as antigen. The pPhtCPB phagemid was constructed by ligation of the double stranded oligonucleotide (SEQ ID NO: 55) with the appropriate restriction enzyme overhang sequences into KpnI and MunI restricted pPhtCTLD phagemid DNA. The pPhtCBP phages derived upon infection with the helper phages displays only the wild type M13 gene III protein because of the translation termination codons introduced into the CTLD coding region of the resulting pPhtCPB phagemid (SEQ ID NO: 56).
The selection experiments were performed in 96 well micro titer plates using standard procedures. Briefly, in each well 3 μg of human plasminogen in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH) or 100 μL PBS (for analysis of non specific binding) was used for over night coating at 4° C. and at 37° C. for one hour. After washing once with PBS, wells were blocked with 400 μL PBS and 3% non fat dried milk for one hour at 37° C. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of phages suspended in 100 μL PBS, 3% non fat dried milk. The phages were allowed to bind at 37° C. for one hour before washing three times with PBS, Tween 20 and three times with PBS. Bound phages were eluted from each well by trypsin digestion in 100 μL (1 mg/mL trypsin in PBS) for 30 min. at room temperature, and used for infection of exponentially growing E. coli TG1 cells before plating and titration on 2×TY agar plates containing 20 glucose and 0.1 mg/mL ampicillin.
Initially (round 1), 1012 PhtCTLD phages (A series), a mixture of 1010 PhtCTLD phages and 1011 PhtCPB phages (B series), or a mixture of 106 PhtCTLD and 1011 PhtCPB phages (C series) were used. In the following round (round 2) 1011 phages of the output from each series were used. Results from the two rounds of selection are summarised in Table 4.
Phagemid DNA from 12 colonies from the second round of plating together with 5 colonies from a plating of the initial phage mixtures was isolated and the nucleotide sequence of the CTLD region determined. From the initial 1/10 mixture (B series) of PhtCTLD/PhtCPB one out of five were identified as the CTLD sequence. From the initial 1/105 mixture (C series) all five sequences were derived from the pPhtCPB phagemid. After round 2 nine of the twelve sequences analyzed from the B series and all twelve sequences from the C series were derived from the pPhtCTLD phagemid.
Model Selection of CTLD-Phages on Plasminogen.
II: Elution by 0.1 M Triethylamine After Panning.
In order to demonstrate that tetranectin derived CTLD-bearing phages can be selected from a population of phages, mixtures of PhtCTLD phages isolated from a E. coli TG1 culture transformed with the phagemid pPhtCTLD (cf, EXAMPLE 1) after infection with M13K07 helper phage and phages isolated from a culture transformed with the phagemid pPhtCPB (cf, EXAMPLE 6) after infection with M13K07 helper phage at ratios of 1:102 and 1:106, respectively were used in a selection experiment using panning in 96-well Maxisorb micro-titerplates (NUNC, Denmark) and with human plasminogen as antigen using standard procedures.
Briefly, in each well 3 μg of human plasminogen in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH) or 100 μL PBS (for analysis of non specific binding) was used for over night coating at 4° C. and at 37° C. for one hour. After washing once with PBS, wells were blocked with 400 L PBS and 3% non fat dried milk for one hour at 37° C. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of phages suspended in 100 μL PBS, 3% non fat dried milk. The phages were allowed to bind at 37° C. for one hour before washing 15 times with PBS, Tween 20, and 15 times with PBS. Bound phages were eluted from each well by 100 μL 0.1 M triethylamine for 10 min at room temperature, and upon neutralisation with 0.5 vol. 1 M Tris-HCl pH 7.4, used for infection of exponentially growing E. coli TG1 cells before plating and titration on 2×TY agar plates containing 20 glucose and 0.1 mg/mL ampicillin.
Initially (round 1) 1012 PhtCTLD phages (A series), a mixture of 109 PhtCTLD phages and 1011 PhtCPB phages (B series), or a mixture of 105 PhtCTLD and 1011 PhtCPB phages (C series) were used. In the following round (round 2) 1011 phages of the output from each series were used. Results from the two rounds of selection are summarised in Table 5.
Phage mixtures from the A and the B series from the second round of selection were grown using a standard procedure, and analyzed for binding to plasminogen in an ELISA-type assay. Briefly, in each well 3 μg of plasminogen in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH) or 100 μL PBS (for analysis of non specific binding) was used for over night coating at 4° C. and at 37° C. for one hour. After washing once with PBS, wells were blocked with 400 μL PBS and 3% non fat dried milk for one hour at 370C. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of phages suspended in 100 μL PBS, 3% non fat dried milk. The phage mixtures were allowed to bind at 37° C. for one hour before washing three times with PBS, Tween 20, and three times with PBS. After washing, 50 μL of a 1:5000 dilution of a HRP-conjugated anti-gene VIII antibody (Amersham Pharmacia Biotech) in PBS, 3% non fat dried milk was added to each well and incubated at 37° C. for one hour. After binding of the “secondary” antibody wells were washed three times with PBS, Tween 20, and three times with PBS before the addition of 50 μL of TMB substrate (DAKO-TMB One-Step Substrate System, code: 51600, DAKO, Denmark). Reaction was allowed to proceed for 20 min. before quenching with 0.5 vol. 0.5 M H2SO4, and analysis. The result of the ELISA analysis confirmed specific binding to plasminogen of phages in both series (
Selection of Phages From the Library Phtlec-lb002 Binding to Hen Egg White Lysozyme.
1.2*1012 phages, approximately 250 times the size of the original library, derived from the Phtlec-lb002 library (cf, EXAMPLE 4) were used in an experimental procedure for the selection of phages binding to hen egg white lysozyme involving sequential rounds of panning using standard procedures.
Briefly, 30 μg of hen egg white lysozyme in 1 mL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH) or 1 mL PBS (for analysis of non specific binding) was used for over night coating of Maxisorb immunotubes (NUNC, Denmark) at 4° C. and at 37° C. for one hour. After washing once with PBS, tubes were filled and blocked with PBS and 3% non fat dried milk for one hour at 37° C. After blocking tubes were washed once in PBS, 0.1% Tween 20 and three times with PBS before the addition of phages suspended in 1 mL PBS, 3% non fat dried milk. The phages were allowed to bind at 37° C. for one hour before washing six times with PBS, Tween 20 and six times with PBS. Bound phages were eluted from each well by 1 mL 0.1 M triethylamine for 10 min at room temperature, and upon neutralisation with 1 M Tris-HCl pH 7.4, used for infection of exponentially growing E. coli TG1 cells before plating and titration on 2×TY agar plates containing 20 glucose and 0.1 mg/mL ampicillin. In the subsequent rounds of selection approximately 1012 phages derived from a culture grown from the colonies plated after infection with the phages eluted from the lysozyme coated tube were used in the panning procedure. However, the stringency in binding was increased by increasing the number of washing step after phage panning from six to ten.
The results from the selection procedure is shown in Table 7.
Phages were grown from twelve clones isolated from the third round of selection in order to analyse the specificity of binding using a standard procedure, and analyzed for binding to hen egg white lysozyme and human β2-microglobulin in an ELISA-type assay. Briefly, in each well 3 μg of hen egg white lysozyme in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH), or 3 μg of human β2-microglobulin, or 100 μL PBS (for analysis of non specific binding) was used for over night coating at 4° C. and at 37° C. for one hour. After washing once with PBS, wells were blocked with 400 μL PBS and 3% non fat dried milk for one hour at 37° C. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of phages suspended in 100 μL PBS, 3% non fat dried milk. The phages were allowed to bind at 37° C. for one hour before washing three times with PBS, Tween 20 and three times with PBS. After washing, 50 μL of a 1 to 5000 dilution of a HRP-conjugated anti-gene VIII antibody (Amersham Pharmacia Biotech) in PBS, 3% non fat dried milk was added to each well and incubated at 37° C. for one hour. After binding of the “secondary” antibody wells were washed three times with PBS, Tween 20 and three times with PBS before the addition of 50 μL of TMB substrate (DAKO-TMB One-Step Substrate System, code: 51600, DAKO, Denmark). Reaction was allowed to proceed for 20 min before quenching with 0.5 M H2SO4.
Results showing relatively weak but specific binding to lysozyme are summarised in
Construction of the Rat Mannose-Binding Protein CTLD (r-MBP) Derived Phagemid (pPrMBP) and Human Lung Surfactant Protein D CTLD (h-SP-D) Derived Phagemid (pPhSP-D)
The phagemid, pPrMBP, is constructed by ligation of the Sfi I and Not I restricted DNA fragment amplified from cDNA, isolated from rat liver (Drickamer, K., et al., J. Biol. Chem. 1987, 262(6):2582-2589) (with the oligonucleotide primers SfiMBP 5′-CGGCTGAGCGGCCCAGCCGGCCATGGCCGAGCCAAACAAGTTGCATGCCTTCTCC-3′ [SEQ ID NO:62] and NotMBP 5′-GCACTCCTGCGGCCGCGGCTGGGAACTCGCAGAC-3′ [SEQ ID NO:63]) into a Sfi I and Not I precut vector, pCANTAB 5E supplied by Amersham Pharmacia Biotech (code no. 27-9401-01) using standard procedures. Outlines of the resulting pPrMBP is shown in
The phagemid,pPhSP-D, is constructed by ligation of the Sfi I and Not I restricted DNA fragment amplified from cDNA, isolated from human lung (Lu, J., et al., Biochem J. 1992 Jun. 15; 284:795-802) (with the oligonucleotide primers SfiSP-D 5′-CGGCTGAGCGGCCCAGCCGGCCATGGCCGAGCCAAAGAAAGTTGAGCTCTTCCC-3′ [SEQ ID NO:64] and NotSP-D 5′-GCACTCCTGCGGCCGCGAACTCGCAGACCACAAGAC-3′ [SEQ ID NO:65]) into a Sfi I and Not I precut vector, pCANTAB 5E supplied by Amersham Pharmacia Biotech (code no. 27-9401-01) using standard procedures. Outlines of the resulting pPhSP-D is shown in
Construction of the Phage Library PrMBP-lb001
The phage library PrMBP-lb001, containing random amino acid residues corresponding to PrMBP CTLD (SEQ ID NO:59) positions 71 to 73 or 70 to 76 (loop 1) and 97 to 101 or 100 to 101 (loop 4) is constructed by ligation of 20 μg SfiI and NotI restricted pPrMBP phagemid DNA (cf. Example 10) with 10 μg of a SfiI and NotI restricted DNA fragment population encoding the appropriately randomized loop 1 and 4 regions. The DNA fragment population is amplified, from nine assembly reactions combining each of the three loop 1 DNA fragments with each of the three loop 4 DNA fragments as templates and the oligonucleotides Sfi-tag 5′-CGGCTGAGCGGCCCAGC-3′ (SEQ ID NO:74) and Not-tag 5′-GCACTCCTGCGGCCGCG-3′ (SEQ ID NO:75) as primers using standard procedures. Each of the three loop 1 fragments is amplified in a primary PCR reaction with pPrMBP phagmid DNA (cf. Example 10) as template and the oligonucleotides MBPloop1a fo (SEQ ID NO:66), MBPloop1b fo (SEQ ID NO:67)or MBPloop1c fo (SEQ ID NO:68) and SfiMBP (SEQ ID NO:62) as primers, and further amplified in a secondary PCR reaction using Sfi-tag (SEQ ID NO:74) and MBPloop1-tag fo (SEQ ID NO:69). Each of the three DNA loop 4 fragments is amplified in a primary PCR reaction with pPrMBP phagemid DNA (cf. Example 10) as template and the oligonucleotides MBPloop4a rev (SEQ ID NO:71), MBPloop4b rev (SEQ ID NO:72) or MBPloop4c rev (SEQ ID NO:73) and NotMBP (SEQ ID NO:63) as primers using standard procedures and further amplified in a secondary PCR reaction using MBPloop4-tag rev (SEQ ID NO:70) and Not-tag (SEQ ID NO:63). In the oligonucleotide sequences N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively, and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence. The ligation mixture is used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells are plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated over night at 30° C.
Construction of the Phage Library PhSP-D-lb001
The phage library PhSP-D-lb001, containing random amino acid residues corresponding to PhSP-D CTLD insert (SEQ ID NO:61) positions 74 to 76 or 73 to 79 (loop 1) and 100 to 104 or 103 to 104 (loop 4) is constructed by ligation of 20 μg SfiI and NotI restricted pPhSP-D phagemid DNA (cf. Example 10) with 10 of a SfiI and NotI restricted DNA fragment population encoding the appropriately randomized loop 1 and 4 regions. The DNA fragment population is amplified, from nine assembly reactions combining each of the three loop 1 DNA fragments with each of the three loop 4 DNA fragments as templates and the oligonucleotides Sfi-tag 5′-CGGCTGAGCGGCCCAGC-3′ (SEQ ID NO:74) and Not-tag 5′-GCACTCCTGCGGCCGCG-3′ (SEQ ID NO:75) as primers using standard procedures. Each of the three loop 1 fragments is amplified in a primary PCR reaction with pPhSP-D phagemid DNA (cf. Example 10) as template and the oligonucleotides Sp-dloop1a fo (SEQ ID NO:76), Sp-dloop1b fo (SEQ ID NO:77)or Sp-dloop1c fo (SEQ ID NO:78) and SfiSP-D (SEQ ID NO:64) as primers, and further amplified in a PCR reaction using Sfi-tag (SEQ ID NO:74) and Sp-dloop1-tag fo (SEQ ID NO:79) as primers. Each of the three DNA loop 4 fragments is amplified in a primary PCR reaction with pPhSP-D phagemid DNA (cf. Example 10) as template and the oligonucleotides Sp-dloop4a rev (SEQ ID NO:81), Sp-dloop4b rev (SEQ ID NO:82) or Sp-dloop4c rev (SEQ ID NO:83) and NotSP-D (SEQ ID NO:65) as primers using standard procedures and further amplified in a PCR reaction using Sp-dloop4-tag rev (SEQ ID NO:80) and Not-tag (SEQ ID NO:75) as primers. In the oligonucleotide sequences N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively, and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence. The ligation mixture is used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells are plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated over night at 30° C.
Construction of the Phage Library PhtCTLD-lb004
All oligonucleotides used in this example were supplied by DNA Technology (Aarhus, Denmark).
The phage library PhtCTLD-lb004, containing random amino acid residues corresponding to PhtCTLD (SEQ ID NO:15) positions 97 to 102 or 98 to 101(loop 3) and positions 116 to 122 or 118 to 120 (loop 5) was constructed by ligation of 20 μg KpnI and MunI restricted pPhtCTLD phagemid DNA (cf. Example 1) with 10 μg of a KpnI and MunI restricted DNA fragment population encoding the randomized loop 3 and 5 regions. The DNA fragment population was amplified from nine primary PCR reactions combining each of the three loop 3 DNA fragments with each of the three loop 5 DNA fragments. The fragments was amplified with either of the oligonucleotides loop3a (SEQ ID NO:84), loop3b (SEQ ID NO: 85), or loop3c (SEQ ID NO:86) as template and loop5a(SEQ ID NO:87), loop5b(SEQ ID NO:88)or loop5c(SEQ ID NO:89) and loop3-4rev(SEQ ID NO:91) as primers. The DNA fragments were further amplified in PCR reactions, using the primary PCR product as template and the oligonucleotide loop3-4rev (SEQ ID NO:91) and loop3-4-stag fo (SEQ ID NO:90) as primers. All PCR reactions were performed using standard procedures.
In the oligonucleotide sequences N denotes a mixture of 25% of each of the nucleotides T, C, G, and A, respectively and S denotes a mixture of 50% of C and G, encoding the appropriately randomized nucleotide sequence. The ligation mixture was used to transform so-called electrocompetent E. coli TG-1 cells by electroporation using standard procedures. After transformation the E. coli TG-1 cells were plated on 2×TY-agar plates containing 0.2 mg ampicillin/mL and 20 glucose and incubated over night at 30° C.
The size of the resulting library, PhtCTLD-lb004, was determined to 7*109 clones. Sixteen clones from the library were picked and phagemid DNA isolated. The nucleotide sequence of the loop-regions were determined (DNA Technology, Aarhus, Denmark). Thirteen clones were found to contain correct loop inserts and three clones contained a frameshift mutation in the region.
Selection of Phtlec-Phages and PhtCTLD-Phages Binding to the Blood Group A Sugar Moiety Immobilised on Human Serum Albumin
Phages grown from glycerol stocks of the libraries Phtlec-lb001 and Phtlec-lb002 (cf. Example 4) and phages grown from a glycerol stock of the library PhtCTLD-lb003 (cf. Example 5), using a standard procedure, were used in an experiment designed for the selection of Phtlec- and PhtCTLD derived phages with specific affinity to the blood group A sugar moiety immobilized on human serum albumin, A-HA, by panning in 96-well Maxisorb micro-titerplates (NUNC, Denmark) using standard procedures.
Initially, the phage supernatants were precipitated with 0.3 volume of a solution of 20% polyethylene glycol 6000 (PEG) and 2.5 M NaCl, and the pellets re-suspended in TE-buffer (10 mM Tris-HCl pH 8, 1 mM EDTA). After titration on E. coli TG-1 cells, phages derived from Phtlec-lb001 and -lb002 were mixed (#1) in a 1:1 ratio and adjusted to 5*1012 pfu/mL in 2*TY medium, and phages grown from the PhtCTLD-lb003 library (#4) were adjusted to 2.5*1012 pfu/mL in 2*TY medium.
One microgram of the “antigen”, human blood group A trisaccharide immobilised on human serum albumin, A-HA, (Glycorex AB, Lund, Sweden) in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH), in each of three wells, was coated over night at 4° C. and at room temperature for one hour, before the first round of panning. After washing once with PBS, wells were blocked with 300 μL PBS and 3% non fat dried milk for one hour at room temperature. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of a mixture of 50 μL of the phage suspension and 50 μL PBS, 6% non fat dried milk. The phages were allowed to bind at room temperature for two hours before washing eight times with PBS, Tween 20, and eight times with PBS. Bound phages were eluted from each well by trypsin digestion in 100 μL (1 mg/mL trypsin in PBS) for 30 min. at room temperature, and used for infection of exponentially growing E. coli TG1 cells before plating and titration on 2×TY agar plates containing 20 glucose and 0.1 mg/mL ampicillin.
In the second round of selection, 150 μL of crude phage supernatant, grown from the first round output colonies, was mixed with 150 μL PBS, 6% non fat dried milk, and used for panning distributing 100 μL of the mixture in each of three A-HA coated wells, as previously described. Stringency in binding was increased by increasing the number of washing steps from 16 to 32. 300 μL of phage mixture was also used for panning in three wells, which had received no antigen as control.
In the third round of selection, 150 μL of crude phage supernatant, grown from the second round output colonies, was mixed with 150 μL PBS, 6% non fat dried milk, and used for panning distributing 100 μL of the mixture in each of three A-HA coated wells, as previously described. The number of washing steps was again 32. 300 μL of phage mixture was also used for panning in three wells, which had received no antigen as control.
The results from the selection procedure are summarised in Table 8
48 clones from each of the #1 and #4 series were picked and grown in a 96 well microtiter tray and phages produced by infection with M13K07 helper phage using a standard procedure. Phages from the 96 phage supernatants were analyzed for binding to the A-HA antigen and for non-specific binding to hen egg white lysozyme using an ELISA-type assay. Briefly, in each well 1 μg of A-HA in 100 μL PBS (PBS, 0.2 g KCl, 0.2 g KH2PO4, 8 g NaCl, 1.44 g Na2HPO4, 2H2O, water to 1 L, and adjusted to pH 7.4 with NaOH) or 1 μg of hen egg white lysozyme in 100 μL PBS (for analysis of non specific binding) was used for over night coating at 4° C. and at room temperature for one hour. After washing once with PBS, wells were blocked with 300 μL PBS and 3% non fat dried milk for one hour at room temperature. After blocking wells were washed once in PBS and 0.1% Tween 20 and three times with PBS before the addition of 50 μL phage supernatant in 50 μL PBS, 6% non fat dried milk. The phage mixtures were allowed to bind at room temperature for two hours before washing three times with PBS, Tween 20, and three times with PBS. After washing, 50 μL of a 1:5000 dilution of a HRP-conjugated anti-gene VIII antibody (Amersham Pharmacia Biotech) in PBS, 3% non fat dried milk, was added to each well and incubated at room temperature for one hour. After binding of the “secondary” antibody wells were washed three times with PBS, Tween 20, and three times with PBS before the addition of 50 μL of TMB substrate (DAKO-TMB One-Step Substrate System, DAKO, Denmark). Reaction was allowed to proceed for 20 min. before quenching with 0.5 M H2SO4, and analysis. The result of the ELISA analysis showed “hits” in terms of specific binding to A-HA of phages in both series (
From the #1 series 13 hits were identified and 28 hits were identified from the #4 series.
Aspberg, A., Miura, R., Bourdoulous, S., Shimonaka, M., Heinegård, D., Schachner, M., Ruoslahti, E., and Yamaguchi, Y. (1997). “The C-type lectin domains of lecticans, a family of aggregating chondroitin sulfate proteoglycans, bind tenascin-R by protein-protein interactions independent of carbohydrate moiety”. Proc. Natl. Acad. Sci. (USA) 94: 10116-10121
Bass, S., Greene, R., and Wells, J. A. (1990). “Hormone phage: an enrichment method for variant proteins with altered binding properties”. Proteins 8: 309-314
Benhar, I., Azriel, R., Nahary, L., Shaky, S., Berdichevsky, Y., Tamarkin, A., and Wels, W. (2000). “Highly efficient selection of phage antibodies mediated by display of antigen as Lpp-OmpA' fusions on live bacteria”. J. Mol. Biol. 301: 893-904
Berglund, L. and Petersen, T. E. (1992). “The gene structure of tetranectin, a plasminogen binding protein”. FEBS Letters 309: 15-19
Bertrand, J. A., Plgnol, D., Bernard, J-P., Verdier, J-M., Dagorn, J-C., and Fontecilla-Camps, J. C. (1996). “Crystal structure of human lithostathine, the pancreatic inhibitor of stone formation”. EMBO J. 15: 2678-2684
Bettler, B., Texido, G., Raggini, S., Ruegg, D., and Hofstetter, H. (1992). “Immunoglobulin E-binding site in Fc epsilon receptor (Fc epsilon RII/CD23) identified by homolog-scanning mutagenesis”. J. Biol. Chem. 267: 185-191
Blanck, O., Iobst, S. T., Gabel, C., and Drickamer, K. (1996).“Introduction of selectin-like binding specificity into a homologous mannose-binding protein”. J. Biol. Chem. 271: 7289-7292
Boder, E. T. and Wittrup, K. D. (1997). “Yeast surface display for screening combinatorial polypeptide libraries”. Nature Biotech. 15: 553-557
Burrows L, Iobst S T, Drickamer K. (1997) “Selective binding of N-acetylglucosamine to the chicken hepatic lectin”. Biochem J. 324:673-680
Chiba, H., Sano, H., Saitoh, M., Sohma, H., Voelker, D. R., Akino, T., and Kuroki, Y. (1999). “Introduction of mannose binding protein-type phosphatidylinositol recognition into pulmonary surfactant protein A”. Biochemistry 38: 7321-7331
Christensen, J. H., Hansen, P. K., Lillelund, O., and Thogersen, H. C. (1991). “Sequence-specific binding of the N-terminal three-finger fragment of Xenopus transcription factor IIIA to the internal control region of a 5S RNA gene”. FEBS Letters 281: 181-184
Cyr, J. L. and Hudspeth, A. J. (2000). “A library of bacteriophage-displayed antibody fragments directed against proteins of the inner ear”. Proc. Natl. Acad. Sci (USA) 97: 2276-2281
Drickamer, K. (1992). “Engineering galactose-binding activity into a C-type mannose-binding protein”. Nature 360: 183-186
Drickamer, K. and Taylor, M. E. (1993). “Biology of animal lectins”. Annu. Rev. Cell Biol. 9: 237-264
Drickamer, K. (1999). “C-type lectin-like domains”. Curr. Opinion Struc. Biol. 9: 585-590
Dunn, I. S. (1996). “Phage display of proteins”. Curr. Opinion Biotech. 7: 547-553
Erbe, D. V., Lasky, L. A., and Presta, L. G. “Selectin variants”. U.S. Pat. No. 5,593,882
Ernst, W. J., Spenger, A., Toellner, L., Katinger, H.,Grabherr, R. M. (2000). “Expanding baculovirus surface display. Modification of the native coat protein gp64 of Autographa californica NPV”. Eur. J. Biochem. 267: 4033-4039
Ewart, K. V., Li, Z., Yang, D. S. C., Fletcher, G. L., and Hew, C. L. (1998). “The ice-binding site of Atlantic herring antifreeze protein corresponds to the carbohydrate-binding site of C-type lectins”. Biochemistry 37: 4080-4085
Feinberg, H., Park-Snyder, S., Kolatkar, A. R., Heise, C. T., Taylor, M. E., and Weis, W. I. (2000). “Structure of a C-type carbohydrate recognition domain from the macrophage mannose receptor”. J. Biol. Chem. 275: 21539-21548
Fujii, I., Fukuyama, S., Iwabuchi, Y., and Tanimura, R. (1998). “Evolving catalytic antibodies in a phage-displayed combinatorial library”. Nature Biotech. 16: 463-467
Gates, C. M., Stemmer, W. P. C., Kaptein, R., and Schatz, P. J. (1996). “Affinity selective isolation of ligands from peptide libraries through display on a lac repressor “headpiece dimer”. J. Mol. Biol. 255: 373-386
Graversen, J. H., Lorentsen, R. H., Jacobsen, C., Moestrup, S. K., Sigurskjold, B. W., Thogersen, H. C., and Etzerodt, M. (1998). “The plasminogen binding site of the C-type lectin tetranectin is located in the carbohydrate recognition domain, and binding is sensitive to both calcium and lysine”. J. Biol. Chem. 273:29241-29246
Graversen, J. H., Jacobsen, C., Sigurskjold, B. W., Lorentsen, R. H., Moestrup, S. K., Thogersen, H. C., and Etzerodt, M. (2000). “Mutational Analysis of Affinity and Selectivity of Kringle-Tetranectin Interaction. Grafting novel kringle affinity onto the tetranectin lectin scaffold”. J. Biol. Chem. 275: 37390-37396
Griffiths, A. D. and Duncan, A. R. (1998). “Strategies for selection of antibodies by phage display”. Curr. Opinion Biotech. 9: 102-108
Holtet, T. L., Graversen, J. H., Clemmensen, I., Thogersen, H. C., and Etzerodt, M. (1997). “Tetranectin, a trimeric plasminogen-binding C-type lectin”. Prot. Sci. 6: 1511-1515
Honma, T., Kuroki, Y., Tzunezawa, W., Ogasawara, Y., Sohma, H., Voelker, D. R., and Akino, T. (1997). “The mannose-binding protein A region of glutamic acid185-alanine221 can functionally replace the surfactant protein A region of glutamic acid195-phenylalanine228 without loss of interaction with lipids and alveolar type II cells”. Biochemistry 36: 7176-7184
Huang, W., Zhang, Z., and Palzkill, T. (2000). “Design of potent beta-lactamase inhibitors by phage display of beta-lactamase inhibitory protein”. J. Biol. Chem. 275: 14964-14968
Hufton, S. E., van Neer, N., van den Beuken, T., Desmet, J., Sablon, E., and Hoogenboom, H. R. (2000). “Development and application of cytotoxic T lymphocyte-associated antigen 4 as a protein scaffold for the generation of novel binding ligands”. FEBS Letters 475: 225-231
Håkansson, K., Lim, N. K., Hoppe, H-J., and Reid, K. B. M. (1999). “Crystal structure of the trimeric alpha-helical coiled-coil and the three lectin domains of human lung surfactant protein D”. Structure Folding and Design 7: 255-264
Iobst, S. T., Wormald, M. R., Weis, W. I., Dwek, R. A., and Drickamer, K. (1994). “Binding of sugar ligands to Ca(2+)-dependent animal lectins. I. Analysis of mannose binding by site-directed mutagenesis and NMR”. J. Biol. Chem. 269: 15505-15511
Iobst, S. T. and Drickamer, K. (1994). “Binding of sugar ligands to Ca(2+)-dependent animal lectins. II. Generation of high-affinity galactose binding by site-directed mutagenesis”. J. Biol. Chem. 269: 15512-15519
Iobst, S. T. and Drickamer, K. (1996). “Selective sugar binding to the carbohydrate recognition domains of the rat hepatic and macrophage asialoglycoprotein receptors”. J. Biol. Chem. 271: 6686-6693
Jaquinod, M., Holtet, T. L., Etzerodt, M., Clemmensen, I., Thogersen, H. C., and Roepstorff, P. (1999). “Mass Spectrometric Characterisation of Post-Translational Modification and Genetic Variation in Human Tetranectin”. Biol. Chem. 380: 1307-1314
Kastrup, J. S., Nielsen, B. B., Rasmussen, H., Holtet, T. L., Graversen, J. H., Etzerodt, M., Thogersen, H. C., and Larsen, I. K. (1998). “Structure of the C-type lectin carbohydrate recognition domain of human tetranectin”. Acta. Cryst. D 54: 757-766
Kogan, T. P., Revelle, B. M., Tapp, S., Scott, D., and Beck, P. J. (1995). “A single amino acid residue can determine the ligand specificity of E-selectin”. J. Biol. Chem. 270: 14047-14055
Kolatkar, A. R., Leung, A. K., Isecke, R., Brossmer, R., Drickamer, K., and Weis, W. I. (1998). “Mechanism of N-acetylgalactosamine binding to a C-type animal lectin carbohydrate-recognition domain”. J. Biol. Chem. 273: 19502-19508
Lorentsen, R. H., Graversen, J. H., Caterer, N. R., Thogersen, H. C., and Etzerodt, M. (2000). “The heparin-binding site in tetranectin is located in the N-terminal region and binding does not involve the carbohydrate recognition domain”. Biochem. J. 347: 83-87
Marks, J. D., Hoogenboom, H. R., Griffiths, A. D., and Winter, G. (1992). “Molecular evolution of proteins on filamentous phage. Mimicking the strategy of the immune system”. J. Biol. Chem. 267: 16007-16010
Mann K, Weiss I M, Andre S, Gabius H J, Fritz M. (2000). “The amino-acid sequence of the abalone (Haliotis laevigata) nacre protein perlucin. Detection of a functional C-type lectin domain with galactose/mannose specificity”. Eur. J. Biochem. 267: 5257-5264
McCafferty, J., Jackson, R. H., and Chiswell, D. J. (1991). “Phage-enzymes: expression and affinity chromatography of functional alkaline phosphatase on the surface of bacteriophage”. Prot. Eng. 4: 955-961
McCormack, F. X., Kuroki, Y., Stewart, J. J., Mason, R. J., and Voelker, D. R. (1994). “Surfactant protein A amino acids Glu195 and Arg197 are essential for receptor binding, phospholipid aggregation, regulation of secretion, and the facilitated uptake of phospholipid by type II cells”. J. Biol. Chem. 269: 29801-29807
McCormack, F. X., Festa, A. L., Andrews, R. P., Linke, M., and Walzer, P. D. (1997). “The carbohydrate recognition domain of surfactant protein A mediates binding to the major surface glycoprotein of Pneumocystis carinii”. Biochemistry 36: 8092-8099
Meier, M., Bider, M. D., Malashkevich, V. N., Spiess, M., and Burkhard, P. (2000). “Crystal structure of the carbohydrate recognition domain of the H1 subunit of the asialoglycoprotein receptor”. J. Mol. Biol. 300: 857-865
Mikawa, Y. G., Maruyama, I. N., and Brenner, S. (1996). “Surface display of proteins on bacteriophage lambda heads”. J. Mol. Biol. 262: 21-30
Mio H, Kagami N, Yokokawa S, Kawai H, Nakagawa S, Takeuchi K, Sekine S, Hiraoka A. (1998). “Isolation and characterization of a cDNA for human mouse, and rat full-length stem cell growth factor, a new member of C-type lectin superfamily”. Biochem. Biophys. Res. Commun. 249: 124-130
Mizuno, H., Fujimoto, Z., Koizumi, M., Kano, H., Atoda, H., and Morita, T. (1997). “Structure of coagulation factors IX/X-binding protein, a heterodimer of C-type lectin domains”. Nat. Struc. Biol. 4: 438-441
Ng, K. K., Park-Snyder, S., and Weis, W. I. (1998a). “Ca2+-dependent structural changes in C-type mannose-binding proteins”. Biochemistry 37: 17965-17976
Ng, K. K. and Weis, W. I. (1998b). “Coupling of prolyl peptide bond isomerization and Ca2+ binding in a C-type mannose-binding protein”. Biochemistry 37: 17977-17989
Nielsen, B. B., Kastrup, J. S., Rasmussen, H., Holtet, T. L., Graversen, J. H., Etzerodt, M., Thogersen, H. C., and Larsen, I. K. (1997). “Crystal structure of tetranectin, a trimeric plasminogen-binding protein with an alpha-helical coiled coil”. FEBS Letters 412: 388-396
Nissim A., Hoogenboom, H. R., Tomlinson, I. M., Flynn, G., Midgley, C., Lane, D., and Winter, G. (1994). “Antibody fragments from a ‘single pot’ phage display library as immunochemical reagents”. EMBO J. 13: 692-698
Ogasawara, Y. and Voelker, D. R. (1995). “Altered carbohydrate recognition specificity engineered into surfactant protein D reveals different binding mechanisms for phosphatidylinositol and glucosylceramide”. J. Biol. Chem. 270: 14725-14732
Ohtani, K., Suzuki, Y., Eda, S., Takao, K., Kase, T., Yamazaki, H., Shimada, T., Keshi, H., Sakai, Y., Fukuoh, A., Sakamoto, T., and Wakamiya, N. (1999). “Molecular cloning of a novel human collectin from liver (CL-L1)”. J. Biol. Chem. 274: 13681-13689
Pattanajitvilai, S., Kuroki, Y., Tsunezawa, W., McCormack, F. X., and Voelker, D. R. (1998). “Mutational analysis of Arg197 of rat surfactant protein A. His197 creates specific lipid uptake defects”. J. Biol. Chem. 273: 5702-5707
Poget, S. F., Legge, G. B., Proctor, M. R., Butler, P. J., Bycroft, M., and Williams, R. L. (1999). “The structure of a tunicate C-type lectin from Polyandrocarpa misakiensis complexed with D-galactose”. J. Mol. Biol. 290: 867-879
Revelle, B. M., Scott, D., Kogan, T. P., Zheng, J., and Beck, P. J. (1996). “Structure-function analysis of P-selectin-sialyl LewisX binding interactions. Mutagenic alteration of ligand binding specificity”. J. Biol. Chem. 271: 4289-4297
Sano, H., Kuroki, Y., Honma, T., Ogasawara, Y., Sohma, H., Voelker, D. R., and Akino, T. (1998). “Analysis of chimeric proteins identifies the regions in the carbohydrate recognition domains of rat lung collectins that are essential for interactions with phospholipids, glycolipids, and alveolar type II cells”. J. Biol. Chem. 273: 4783-4789
Schaffitzel, C., Hanes, J., Jermutus, L., and Placktun, A. (1999). “Ribosome display: an in vitro method for selection and evolution of antibodies from libraries”. J. Immunol. Methods 231: 119-135
Sheriff, S., Chang, C. Y., and Ezekowitz, R. A. (1994). “Human mannose-binding protein carbohydrate recognition domain trimerizes through a triple alpha-helical coiled-coil”. Nat. Struc. Biol. 1: 789-794
Sørensen, C. B., Berglund, L., and Petersen, T. E. (1995). “Cloning of a cDNA encoding murine tetranectin”. Gene 152: 243-245
Torgersen, D., Mullin, N. P., and Drickamer, K. (1998). “Mechanism of ligand binding to E- and P-selectin analyzed using selectin/mannose-binding protein chimeras”. J. Biol. Chem. 273: 6254-6261
Tormo, J., Natarajan, K., Margulies, D. H., and Mariuzza, R. A. (1999). “Crystal structure of a lectin-like natural killer cell receptor bound to its MHC class I ligand”. Nature 402: 623-631
Tsunezawa, W., Sano, H., Sohma, H., McCormack, F. X., Voelker, D. R., and Kuroki, Y. (1998). “Site-directed mutagenesis of surfactant protein A reveals dissociation of lipid aggregation and lipid uptake by alveolar type II cells”. Biochim. Biophys. Acta 1387: 433-446
Weis, W. I., Kahn, R., Fourme, R., Drickamer, K., and Hendrickson, W. A. (1991). “Structure of the calcium-dependent lectin domain from a rat mannose-binding protein determined by MAD phasing”. Science 254: 1608-1615
Weis, W. I., and Drickamer, K. (1996). “Structural basis of lectin-carbohydrate recognition”. Annu. Rev. Biochem. 65: 441-473
Whitehorn, E. A., Tate, E., Yanofsky, S. D., Kochersperger, L., Davis A., Mortensen, R. B., Yonkovic, S., Bell, K., Dower, W. J., and Barrett, R. W. (1995). “A generic method for expression and use of “tagged” soluble versions of cell surface receptors“. Bio/Technology 13: 1215-1219
Wragg, S. and Drickamer, K. (1999). “Identification of amino acid residues that determine pH dependence of ligand binding to the asialoglycoprotein receptor during endocytosis”. J. Biol. Chem. 274: 35400-35406
Zhang, H., Robison, B., Thorgaard, G. H., and Ristow, S. S. (2000). “Cloning, mapping and genomic organization of a fish C-type lectin gene from homozygous clones of rainbow trout (Oncorhynchos Mykiss)”. Biochim. et Biophys. Acta 1494: 14-22
| Number | Date | Country | Kind |
|---|---|---|---|
| 2000 01872 | Dec 2000 | DK | national |
This application is a continuation of U.S. patent application Ser. No. 11/633040, filed Dec. 4, 2006, now U.S. Pat. No. 8,017,559, which is a divisional of U.S. patent application Ser. No. 10/450,472, filed Jun. 13, 2003, which is a national phase application of International Application PCT/DK01/00825, filed Dec. 13, 2001, which claims priority to Denmark application PA 2000 01872, filed Dec. 13, 2000 and U.S. Application No. 60/272,098, filed Feb. 28, 2001. The entire contents of the above-referenced applications are hereby incorporated by reference herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 60272098 | Feb 2001 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10450472 | Jun 2003 | US |
| Child | 11633040 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11633040 | Dec 2006 | US |
| Child | 13156138 | US |
