Patent Application
20080267944
This invention refers to the process for obtaining the recombinant prothrombin activating protease (rLopap) in monomeric form; the recombinant prothrombin activating protease (rLopap) as well as its amino acid sequence; the use of this protease for depleting blood fibrinogen and the diagnosis kit for dysprothrombinemias.
The Lonomia genus is known for causing a systemic envenoming as a consequence of its venom inoculation through the skin, presenting hemorrhagic manifestations of variable intensity, sometimes casing the death of the exposed subject (Lorini, 1999). The Walker Lonomia obliqua species (Lemaire, 1972) has caused epidemic dimension accidents since 1989 in restricted areas in the south of Brazil (Rio Grande do Sul, Santa Catarina and Paraná) (BRAZIL, 1998).
The exposed patients, among other symptoms, show mainly, blood dyscrasia signs (alteration in the proportion of the blood elements) after a period that may vary from 1 to 48 hours, followed or not by hemorrhagic manifestations and could even resulting in death (Kelen et al, 1995; Brazil, 1998).
Recently, Zannin et. al. determined the coagulation parameters and the plasma fibrinolysis of 105 patients and verified, corroborating with some existing data, that the accident affects the mechanisms of coagulation and fibrinolysis. These results indicate an intense consumption coagulopathy that can be attributed to components of the venom present in the bristles of the Lonomia obliqua caterpillar, with powerful procoagulant action and secondary activation of the fibrinolysis (Zannin et. al., 2002).
The Lonomia obliqua caterpillar venom presents some components that interfere in the coagulation system. In the L. obliqua bristles extract the presence of prothrombin activators and of Factor X was already described (Donato et. al., 1998; Kelen et. al., 1995).
The inventors of this patent requesting isolated and characterized a prothrombin activating protease of 69 kDa, named Lopap (Lonomia obliqua prothrombin activator protease). It has serineprotease characteristics and procoagulant activity in rats, depleting blood of fibrinogen and altering in only 30% the number of platelets, although completely inhibiting the aggregation function of the platelets induced by collagen for increasing the PGI2 levels.
Lopap, when injected in rats per intraperitoneal administration, develops thrombi in venules and arterioles, causing polymorphonuclear migration to the lungs and kidneys (Reis et. al., 1999, Reis et al, 2001 a, b).
Recently it could be verified that Lopap acts in endothelial cells (HUVECs), as an inductor of the adhesion molecules expression like ICAM-1 and E-selectin, however it does not express VCAM. It does also induce the increase of IL-8 and of PGI2. The non-expression of VCAM suggests that the pro-inflammatory action of Lopap can not be compared to the TNF-α or to the thrombin on endothelial cells. High concentrations of PGI2 can also be acting as platelet anti-aggregating.
It was also verified that the thrombin produced by Lopap is functional and inhibited by Antithrombin III (AT) and it is able to aggregate platelets as well as to coagulate plasma and fibrinogen, suggesting to be similar to the α-thrombin (Chudzinski-Tavassi et al, 2001).
The L. obliqua bristles extract is effective in the experimental prevention of venous thrombosis in rats (Prezoto et. al, 2002), justifying the studies using purified venom fractions for elucidating the mechanisms of this effect.
During this study, a cDNA library in pGEM11zf+plasmids was built and through the use of specific degenerated initiator oligonucleotides obtained from the N-terminus portion of the native protein, a clone, correspondent to Lopap was isolated and its sequence was determined. The sequence of amino acids deduced from the cDNA was aligned with other sequences of the CLUSTAL W program from the “GenBank”.
Lopap presented 37% of identity with BBP BILIN-BINDING PROTEIN of Pieris brassicae; 34% with ApoD —APOLIPOPROTEIN D PRECURSOR of Homo sapiens; 35% with INS-A —INSECTICYANIN A of Manduca sexta; 22% with CC-A2—A2 CRUSTACYANIN A2 SUB-UNITY of Homarus gammarus; 26% with CC-C1.—C1-CRUSTACYANIN C1 SUB-UNITY of Homarus gammarus, and 27% with PURP.—PURPURIN PRECURSOR of Gallus gallus (gi 131549).
The lipocalins (from the Greek “lipos”=fat and “calyx”=goblet) are part of a large group, presented in several species, always expanding and showing a great functional and structural variety. In general they are small proteins varying between 160 and 180 amino acids, presenting common characteristics (Flower et. al, 2000).
These proteins show few similarities one another (around 20%), however they contain two highly conserved domains (eight amino acids residues bound by hydrogen bridges to a “β-barrel” region) allowing to classify them as lipocalins. These regions are responsible for the high similarity of its secondary and tertiary structures.
The lipocalins are able to bind themselves to the molecules (especially the hydrophobic as retinol) for presenting a hydrophobic “β-barrel”-kind region, composed by a cavity inside and a loop outside and containing a binding site to different ligands. The diversity of these cavities and “loops” bring to each protein the possibility of accommodating ligands of different sizes, forms and chemical characteristics.
From the sequence obtained by cDNA, an approach for studying the Lopap structural model using the Swiss PDB Viewer 3.7 (b2) program and the Swiss Model Server was conducted. What was found is a typical lipocalin family structure, however it was not possible to visualize a serine protease site through this modeling.
Lipocalin family member proteins were not described in literature as having function of a prothrombin activating protease. Different from other activators of animal venoms, rLopap hydrolyses the prothrombin, generating fragments (prethrombin 2, thrombin and fragments 1.2 and fragments 1 and 2), independently of its prothrombinase complex components. This kind of fragmentation promotes a slower formation of thrombin, enabling a better control of it and impeding its action. Moreover, for promoting cellular responses concerning the endothelial level as the expression of NO, PGI2, rLopap is different from other known activators since it can modulate platelet aggregation response. Besides that, this protein has the advantage to be easily obtained in its recombinant form, when compared to other venom prothrombin activators.
Based on the rLopap capacity to activate prothrombin, a dosage kit of these factor concentrations in the plasma can be prepared. After the rLopap incubation with the diluted human plasma, the thrombin formed is determined by the hydrolyzes of a specific chromogenic or fluorogenic substrate (on the market, for instance S2238 of Chromogenix presenting the sequence H-D-phenylalanyl-L-pipecolyl-L-arginyl-p-nitroanilide or that can be synthesized as the case of Abz-FFNPRTFGSGQ-EDDnp). When referring to the absorbency of chromogenic substrates, measured in 405 nm, it shows to be proportional to that of the sample prothrombin activity and it is comparable to the standard human plasma curve on the market.
Based on the defibrinogenase potential of the protein activating activity without altering the platelet number and in the structural differences that allow considering Lopap as a new prothrombin activator, a patent request was deposited by the same authors, concerning this protein —PI 02002698.
The PI 0200269-8, in general lines, describes a purifying process of soluble proteins from the bristles of the Lonomia obliqua caterpillar with prothrombin activating activity, a process for the partial determination of the amino acids sequence of the referred prothrombin activator, a process for determining this prothrombin activating activity of fraction II as well as the prothrombin activator and the use of this activator.
Following the same research approach toward the protein mentioned above, the inventors are now presenting the Lopap in its recombinant form and with adequate activity for allowing clinical Pharmacology essays.
According to this invention, Lopap was subcloned in expression vector and expressed in E. coli.
For conducting this invention the following items were used:
Lineage: Escherichia coli;
1) Strain DH5α: ø80 dlacZΔM15, recA1, endA1, gyrA96, thi-1, hsdR17 (rk−, mk+) SupE44, relA1, deoR Δ(lac ZYA-arg I) u169.
2) Strain BL21 (DE3): F′, ampT, hsdSB(r8−, m8−), dcm, gal (DE3). The DE3 bacteriophage contains the RNA polymerize gene of the T7 phage under the control of the Lac UV5 promoter, inducible by isopropil-thio-β-galactoside (IPTG).
Plasmids:
1) pGEM-11Zf (+): vector digested with EcoRI e Not I used in the plasmid library construction. PROMEGA Technical Manual, 1999.
2) “easy” pGEM-T: The “easy” pGEM-T plasmid contains the T7 and SP6 promoters flanked the MCS (“multiple cloning site”) region for sub-cloning the PCR products. PROMEGA Technical Manual, 1999.
3) pAE: expression vector derived from pRSETA (Invitrogen) and from pET3-His (Chen, 1994) constructed in the Molecular Biotechnology Laboratory of the Institute Butantan (Ramos et. al, 2003).
The pAE is a high expression vector that combines the T7 promoter efficiency and the high number of pRSETA plasmid copies with an N-terminus fusion of six histidines non-removable from pET3-His, allowing the purification of recombinant proteins through the IMAC (“Immobilized Metal Affinity Chromatography”). The addition of this small fusion does not interfere in the activity of the majority of the studied recombinant proteins.
For the Synthesis of the initiator oligonucleotides in PCR reactions, the process was conducted as follows:
The “sense” oligonucleotides (P1 and P2) were obtained from the N-terminus sequence of the protein (
For the mRNA preparation, the procedures were defined as follows:
The caterpillars were anesthetized in CO2 (dry ice) condition and their spicules were cut (2.7 g) and placed in a sterile plastic tube previously weighed, immerse in liquid nitrogen. The spicules were grounded in a mortar, after being treated with DEPC (diethyl pyrocarbonate) for eliminating RNAses, using dry ice and liquid nitrogen until turning into a fine powder.
The spicule powder was used for obtaining the total RNA using preferably the Triazol method in accordance with the methodology described in the manual of its manufacturer.
The accessories of the electrophoresis system were treated with hydrogen peroxide (H2O2) 3%, for eliminating RNAses and were washed with sterilized DEPC treated water. A 1.5% agarose gel in 10 mM, pH 7.0 sodium phosphate buffer was deposited in the regular system. Two samples containing 10 or 15 μl of total RNA (16.7 ng/μl), 5 μl of sample buffer and DEPC treated H2O for a final volume of 25 μl, were applied in the gel. The sample migration was conducted at 5 V/cm until bromophenol would reach ⅔ of the gel.
Purification of the mRNA in Oligo (dT) Cellulose Affinity Column
The mRNA was purified in oligo dT cellulose affinity column washed with NaOH 0.1 N and balanced with 1 ml of Tris-HCl 10 mM, EDTA 1 mM, NaCl 300 mM, SDS 0.1%, pH 7.0 buffer.
3 ml of this buffer was added to the total RNA followed by the incubation at 70° C. for 5 minutes, cooling it in ice for another 5 minutes and applied in the affinity column. The column was drained by gravity and washed using more 4 ml of the buffer for eliminating every RNA that was not a mRNA. The mRNA was eluded with 1.5 ml of Tris-HCl 10 mM, EDTA 1 mM, SDS 0.1%, pH 7.0 buffer and collected in clean treated tube, heated at 70° C. for 5 minutes and cooled in ice for another 5 minutes. After incubating the material for 20 minutes at room temperature, 90 μl of NaCl 5 M was added to it and again it was applied in the column re-balanced with the buffer. What was obtained after another washing using 4 ml of the buffer and eluting the material with 1.5 ml of elution buffer, was precipitated “overnight” with 90 μl of NaCl 5 M and 3 ml of absolute ethyl alcohol at −80° C. The material was then centrifuged in 7000 g for 20 minutes at 4° C. and the supernatant was rejected. The mRNA was washed with 1 ml of ethyl alcohol 75% and centrifuged in 7000 g for 2 minutes at 4° C.
After drying it, the precipitate mRNA was re-suspended in 20 μl of DEPC treated H2O and maintained at −80° C.
The mRNA Quantification
For a final volume of 500 μl, 2 μl of mRNA in 498 μl of sterilized H2O milli-Q was added to it. The optical density readings were conducted in 260 and 280 nm in quartz cuvets of 500 μl. The mRNA concentration was calculated using the equation:
[RNA]=A260×D×40μg/ml
Concerning the construction of the cDNA library, the following procedures were performed:
The cDNA library was constructed from 4.0 μg of isolated mRNA, using preferably the SuperScrip™ Plasmid System for cDNA Synthesis and Plasmid Cloning (Life Technologies) modified kit.
4.0 μg of mRNA was diluted in 6 μl of DEPC treated H2O in which 1.5 μl of NotI adaptation primer was added and then it was heated at 70° C. for 10 minutes, cooled in ice bath and quickly centrifuged. 4 μl of first strain buffer 5×, 2 μl of DTT 0.1 M, 1 μl of mixture of dNTP 10 mM and 0.5 μl of H2O were added to the tube. The reaction was homogenized, quickly centrifuged and balanced at 44° C. for 2 minutes. 5 μl of Super Script II RT enzyme was added and the mixture was incubated at 44° C. for more 90 minutes. A 4° C.-cooling process interrupted the reaction.
It was added to the mixture of the first strain reaction, 91 μl of H2O, 30 μl of the second strain buffer, 3 μl of dNTP 10 mM mixture, 1 μl of E. coli DNA ligase 10 U/μl, 4 μl of E. coli DNA polymerase I 10 U/ml and 1 μl of E coli RNAase H (2 U/μl). After gently swirling the mixture, it was incubated at 16° C. for 2 hours and added to it 2 μl of T4 DNA polymerase I conducting more 5 minutes of incubation at the same temperature. The reaction was interrupted by cooling process in ice and by adding 10 μl of EDTA 0.5 M.
All the reaction in the second strain added with 17 μl of Ficoll xylene cyanol free was applied in agarose gel 1% and after 1 cm of sample migration in 80 V in electrophoresis system two bands were cut out of the gel. One containing fragments between 400 and 800 pb (low molecular weight—BA) and the other with fragments over 800 pb (high molecular weight—BB).
The DNA was purified from the gel using preferably the Concert Gel Extraction Systems (Life Technologies) kit, the cDNA eluded with 50 μl of H2O heated at 65° C. and reduced into 30 μl using a concentration process.
Binding cDNA to the EcoRI Adaptors
It was added to the reaction tube, 10 μl of T4 DNA ligase 5× buffer, 5 μl of Eco RI (Amersham) adaptors and 5 μl of T4 DNA ligase with posterior incubation at 16° C. for 16 hours. Right after that, the reaction was heated at 65° C. for 10 minutes and cooled in ice. After adding 2 μl of the ATP solution and 2 μl of the T4 polymerase kinase, the reaction was incubated for 30 minutes at 37° C.
The cDNA was extracted using 55 μl of phenol/chloroformium/alcohol isoamilic (25:24:1), swirled and centrifuged in 14000 g for 5 minutes at room temperature. The superior aqueous phase was transferred to another tube and added with 2 volumes of absolute ethanol and 1 volume of 3-M sodium acetate and cooled at −80° C. for 1 hour. After centrifuged in 14000 g for 20 minutes and washed with 500 μl of ethanol 70%, the cDNA was dried in flow for about 5 minutes.
Digestion with NotI
It was added to the precipitated, 41 μl of H2O, 5 μl of REact reaction buffer, 4 μl of NotI, gently homogenized and followed by incubation for 2 hours at 37° C.
50 μl of the reactions (of high and low molecular weight fragments) were applied in agarose gel 1% and after electrophoresis, the bands were cut out of the gel. The cDNAs of high and low weights were purified and eluded with 50 μl of H2O as described in the first size screening (Screening of fragments sizes in agarose gel).
Unidirectional Binding from the cDNA to the pGEM11Zf(+) Vector
The two fractions (14 μl), of high and low weights were added with 4 μl of T4 DNA ligase buffer, 1 μl of clonage vector, preferentially pGEM11Zf(+) (previously digested with the EcoR I—Not I enzymes) (
The bacterial transformation process of this invention follows the procedure described below:
DNAs of high and low weights (2 μl) were added to 50 μl of calcium competent bacteria (DH5α) prepared in accordance with the Inoue et al. (1990) method being maintained at −80° C. and previously defrosted in ice for 15 minutes. The solutions were incubated for 30 minutes in ice and afterwards submitted to a heating shock of 42° C. for 2 minutes and again in ice for 5 minutes.
350 μl of SOC medium was added to the transformed bacteria and then transferred to aerated tubes being incubated at 37° C. under swirling conditions (220 rpm/min) for 90 minutes. 200 μl of cDNA of high and low molecular weights was placed in plates with 2YT-ampicillin medium. These plates were incubated for 18 hours at 37° C. 20 colonies containing high weight inserts and 20 containing low weight ones, were incubated in two plates at 37° C. in 2.5 ml of 2YT-ampicilina 100 μg/ml medium for 18 hours under swirling condition of 200 rpm. The cDNAs were purified using preferably the mini-prep Concert Rapid Plasmid (Life Technologies) kit eluded with 50 μl of TE at 65° C.
For analyzing the library concerning the plasmids, the following procedure was taken:
The plasmids (4 μl) were digested at 37° C. for 2 hours in presence of 1 μl of specific reaction buffer, 4 μl of water, 0.5 μl of EcoRI (10 U/μl) enzyme. The 0.5 μl of HindIII (10 U/μl) and the fragments generated were analyzed in agarose gel 1% with ethidium bromide. All the analyzed plasmids were submitted to sequencing process.
Aiming to obtain the amplification of the library, mixtures containing 50 μl of DH5α calcium-competent bacteria and 5 μl of high or low molecular weight (BA or BB) DNA bound to the clonage vector were incubated for 30 min in ice, for 2 min at 42° C. After that, they were returned in ice for another 5 min. After that, 10 ml of 2YT/ampicilina 100 μg/ml medium was added to them. These solutions were gently homogenized and aliquots of 2.5 ml were transferred by pipettes to deaerated tubes and incubated at 37° C. for 18 h. After that the plasmidial DNA was extracted using mini-preps columns, eluded with 50 μl of H2O at 65° C. and maintained at −20° C.
The PCRs “Polymerase Chain Reaction” prepared for a 50-μl final volume contained 1 μl of dNTPs 10 mM, 5 μl of Buffer for Taq DNA polymerase 10×, 1.5 μl of MgSO4 50 mM and 0.5 μl of TaqDNA polymerase 2.5 U. For amplifying the cDNA that codifies for the prothrombin activating protein, 411 of amplified plasmidial DNA, 4 μl of oligonucleotide P1 10 pM and 2 μl of oligonucleotide SP6 10 pM were used. The reaction was incubated in a thermocycling device in which a denaturation program was conducted initially at 94° C. for 3 min, 30 denaturation cycles (94° C. for 45 seconds), annealing (50° C. for 25 seconds), extension (72° C. for 4 min) and a final extension at 72° C. for 15 min. After that, the samples were applied in agarose gel 1%. After 2 h of electrophoresis migration in 80 V, the bands corresponding to the expected amplification of the products were cut out of the gel and the DNA was extracted and eluded in 30 μl of H2O for binding to a second clonage vector, preferably the “pGEM-T Easy Vector Systems” (PROMEGA).
For performing the binding of the DNA to the “easy” pGEM-T, the following methodology was chosen:
The bindings were conducted for a final volume of 10 μl containing 6 μl of the product PCR (1700 pb), 1 μl of the pGEM-T vector (
The relation vector:insert was calculated in accordance with the following equation:
X=ng of vector; I=Kb of the insert; R=molar relation insert/vector; Y=ng of insert; V=Kb of the vector.
Strains of DH5α E. coli were incubated with 5 μl of the vector-insert binding reaction and placed in plates. Out of the formed colonies, 40 were collected for pre-inoculum and “mini-prep” procedures exactly as described in the protocol for the transformation of DH5α-competent E. coli.
Before processing the “mini-preps” reactions, 300 μl of each pre inoculum were submitted to a quick process of phenol:chloroformium purification in accordance with the method described by Beuken et al. (1998). After that, 20 μl of each sample were applied in agarose gel 1%, in TAE 1× buffer. After the electrophoresis running, the gel was stained with ethidium bromide solution of 0.1 μg/ml for screening the larger recombinant plasmids, under UV light (Sambrook, 1989). The positive clones of the previous item were submitted to the “mini-preps” and eluded with 60 μl of water.
PCR reactions were prepared for a final volume of 10 μl containing 0.2 μl of dNTPs 10 mM, 1.0 μl of buffer for Taq DNA polymerase 10×, 0.3 μl of MgSO4 50 mM, 0.1 μl of Taq DNA polymerase 5 U/μl. For the cDNA amplification, 2 μl of the positive clones purified in the previous item were used, in dilution of 1/50, as templates and 0.8 μl of oligonucleotide P2 10 pM and 0.4 μl of SP6 10 pM as primers. The reaction was incubated in a Perkin-Elmer thermocycling device of model 9600, conducting a initial denaturation program at 94° C. for 3 min, 30 cycles of denaturation (94° C. for 45 seconds), annealing (50° C. for 25 seconds), extension (72° C. for 4 min) and a final extension at 72° C. for 15 min. After that, the samples were applied in agarose gel 1%.
Plasmidial DNA Digestion with Restriction Enzymes
The DNAs of the purified clones amplified by PCR using primer P1 and P2, were digested at 37° C. for 2 h in a solution containing 5 μl of the plasmidial DNA, 2 μl of specific reaction buffer, 0.5 μl of Hind III (10 U/μl), 0.5 of BamH I (10 U/μl) and 12 μl of H2O for a final volume of 20 μl.
The same plasmidial DNAs (5 μl) were incubated in same conditions with 1 μl of specific reaction buffer, 1 μl of EcoR I (10 U/μl) and 12 μl of water.
The digestion products were analyzed in agarose gel 1%. The clones of the library and the DNAs subcloned in “easy” pGEM-T were sequenced.
For performing the sequencing of the DNAs the method of chain termination by dideoxynucleotide was chosen, adapting it to the automatic sequencing process. 400 ng of the plasmidial DNA was prepared through the purification by mini-preps, which was used as molds in the sequencing reaction. T7 and SP6 were used in the described oligonucleotides reactions. After the thermocycling, the amplification products were separated in the DNA gel sequencing of 36 cm of length (4.25% acrylamide:bis-acrylamide in a proportion of 19:1, in 1×TBE and 7 M Urea. The detection system of this device consists in a laser source and a fluorescence detector, set at the lower part of the sequencing gel. Each dNTP emits a specific fluorescence recognized by the detector that sends the message for a computer that will automatically register the position of the nucleotide in the electropherogram. The running was conducted for 7 hours. All the sequenced DNAs were compared with the “GenBank” sequences through the site www.ncbi.nlm.nih.gov/, based on the algorithm of the BLASTx and BLASTn programs, or site www.ebi.ac.uk/ for the FASTA program.
The expression process of the recombinant protein, preferably E. coli strain BL21 (DES), used in this invention follows the procedure lines as listed below:
The positive clones in which sequenced inserts confirmed the Lopap sequence, were incubated in 7 ml of LB/ampicillin at 37° C. for 18 hours, and afterwards they were submitted to the mini-preps and eluded with 50 μl of water.
The purified DNAs were digested at 37° C. for 5 h in a solution containing 20 μl of plasmidial DNA, 5 μl of specific reaction buffer, 1.0 μl of EcoR I (10 U/μl), 1.0 μl of BamH I (10 U/μl) and 23 μl of H2O for a final volume of 50 μl.
After electrophoresis in preparative agarose gel 1%, the bands with around 600 pb were purified from the gel, eluded with 30 μl of H2O and dried by vacuum at 45° C. for 1 h.
The plasmid was re-suspended in 10 μl of H2O and 3.5 μl of it was incubated at 16° C. for 18 h with 3.5 μl of the pAE expression vector (
Aiming to obtain a great amount of soluble recombinant proteins, the BL21 (DE3) strain of the E. coli bacteria was preferably used for expressing this protein. It provides a fast growing, it is easy to be cultured and kept, as well as it presents a high quantity of recombinant proteins. This E. coli strain is lysogenic and does not present the post-translation modification systems.
E. coli cultures transformed preferably by the recombinant expression vector (pAE-clone 14.16) (
For obtaining the expression of the protein (Lopap) of this invention, the following procedures were taken:
E. coli cultures transformed with the expression vector were inoculated in 100 ml of LB/ampicillin (100 μg/μl) medium and incubated at 37° C. until obtaining of a DO600 nm of 0.5. Aliquots of 25 ml were incubated in 4 different bottles with 500 ml of LB/ampicillin (100 μg/μl) for 90 min. at 37° C. IPTG was then added for reaching the final concentration of 1 mM and the incubation was maintained for more 4 h. The medium was then centrifuged in 12000 rpm and frozen at −70° C. for 18 hrs. The cells of the 4 bottles were re-suspended in 70 ml of lysis buffer NaH2PO4 50 mM, NaCl 300 mM, imidazol 10 mM and submitted to a French press of 2000 GAGE for three times and centrifuged in 5000 rpm for 15 min. at 4° C.
The supernatant containing the soluble express protein was centrifuged in 15000 rpm for 30 min for clarification and applied in nickel-sepharose affinity column previously balanced with lysis buffer. The column was washed with buffer imidazol 80 mM, β-mercaptoethanol 5 mM, NaCl 500 mM, Tris HCl 50 mM pH 6.8 and the washing volume was collected. The protein was eluded using Tris-HCl 50 mM pH 8.0, imidazol 1M, NaCl 100 mM with flow of 1 ml/5 min.
The “pellet” (corpuscles) of the medium was submitted to the French press and centrifuged, re-suspended in 20 ml of buffer Tris-HCl 50 mM, Urea 1 M, Triton X-100 1%, pH 8.0 for eliminating hydrophobic components and centrifuged in 5000 rpm for 15 min at 4° C. The separated precipitate was incubated at room temperature for 25° C. with 10 ml of buffer Tris-HCl 50 mM, NaCl 500 mM, Urea 8 M, β-mercaptoethanol 10 mM pH 8.0 for solubilization of the corpuscles. This material was again centrifuged in 4000 rpm for 20 min at 4° C. and the supernatant was added drop by drop into the “refolding” buffer of Tris-HCl 50 mM, NaCl 500 mM, Imidazol 5 mM and β-mercaptoethanol 5 mM pH 8.0 (as an alternative for obtaining the protein with the correct structure. Another approach for reaching this stage was performed using the buffer added with CaCl2 100 mM) with constant swirling at room temperature for 18 h. The material was filtrated and applied for 72 h in a nickel-sepharose column previously balanced with the lysis buffer. The column was washed with 180 ml of buffer Tris-HCl 50 mM, NaCl 500 mM, Imidazol 20 mM pH 6.8 and eluded with Tris-HCl 50 mM pH 8.0, imidazol 1M, NaCl 100 mM with a flow of 1 ml/5 min.
For isolating all the rLopap in its correct form, both the soluble protein and the eluded one provenient from the corpuscles were submitted to a benzamidine-sepharose column in medium of Tris-HCl 20 mM, NaCl 500 mM, pH 8.0 and eluded with glycine 50 mM, pH 3.0. The eluded protein was dialyzed exhaustively against NaCl 3 mM for 48 h.
The eluded protein as well as the aliquots of intermediate phases of the purification process were dosed by the Bradford method (1976) and analyzed by SDS-PAGE.
The recombinant protein obtained was tested concerning its prothrombin activating capacity using purified prothrombin and preferably the S-2238 chromogenic substrate (Chromogenix).
Based on the sequence obtained by cDNA, an approach of Lopap model study was conducted using the Swiss PDB Viewer 3.7 (b2) program and the Swiss Model Server.
For evaluating the “folding” of the recombinant protein, its secondary structure was analyzed by Circular Dichroism spectrometry.
The spectrum (CD) was conducted in a spectropolarimeter at 25° C. between 190 and 300 nm wavelengths. The spectra were accumulated 8 times with a resolution of 1 nm in speed of 200 nm/min.
The recombinant Lopap was diluted in Tris/HCl 20 mM pH=8.0 buffer in a concentration of 1.2 mg/ml. The data were expressed as molar based on the protein concentration.
7.0 μg of mRNA was obtained, out of which 4 μg was used for the construction of a cDNA library.
The mRNA obtained showed to have good quality (1.5:1 relation with proteins) and the analysis in agarose gel revealed a correspondent smir toward the mRNA (
Screening in agarose gel, the plasmid library presented a title of 105 plasmids/μg. Two libraries were constructed in plasmid: one with inserts between 400 and 800 pb (BA) and the other with inserts larger than 800 pb (BB).
From each library 300 clones were randomly selected, that after digestion with EcoR I and Hind III presented a variety of inserts of different sizes. Some of these inserts were digested by the restriction enzymes, producing two fragments in agarose gel (
The product amplifying with the oligonucleotides P1 and SP6 of the BA library (400 to 800 pb) showed a band of approximately 600 pb and another of around 800 pb, while the BB library (larger than 800 pb) showed a band of around 800 pb (
40 clones were collected (example 3), 20 referred to the C1 band (named from C1-1 to C1-20) and the other 20 clones referred to the C2 band (from C2-1 to C2-20), and submitted to the screening process concerning the size of the insert, before the plasmidial DNA purifying through the mini-preps. As demonstrated in
The positive clones from the previous item were amplified with P2 and SP6 and only the clones 2 and 3 of C1 (C1-2 and C-1-3) were positive (
The DNAs C1-2 and C1-3 subcloned in “easy” pGEM-T were aligned after the cleavage of the BamH I site and Hind III and also after the cleavage of the EcoR I sites liberating inserts with around 600 pb (
The clones of the PCR product of 600 pb (C1-2 and C1-3), as well as the clones bound to the pAE expression vector with the same cleavage profile, were sequenced and contained the sequence of the initiator oligonucleotides P1 and P2 and the sequences referring to the 46 residues of the Lopap N-terminus, as well as of the internal fragments previously sequenced. 561 nucleotides were sequenced corresponding to 187 amino acids of the total sequence of the protein (
The insert liberated from the “easy” pGEM-T with the restriction enzymes of BamH I and EcoR I was subcloned in pAE vector with reading phase with the end of the six histidines of this vector.
The recombinant protein with 21 kDa, including the 6 histidine residues added by the pAE vector, was expressed before the induction with IPTG and its production was increased by induction (
The rLopap was dialyzed against EDTA 3 mM and its prothrombin activating activity was tested using S-2238 chromogenic substrate and also in presence of platelets.
The sequence deduced for Lopap showed an identity of around 30% with several proteins of the lipocalin family (
The three-dimensional structure of Lopap, analyzed for modeling and compared to the data banks, showed similarities to a structure quite characteristic to those of the lipocalin family proteins (
Peptides and proteins present a standard spectrum of secondary structure that can be evaluated by Circular Dichroism spectrometry (CD). The most significant and characteristic standard is represented by two α-helices (Holzawarth et al, 1965), in which we can see two negative bands of comparable magnitude close to 222 and 208 nm and one positive band close to 190 nm.
The spectrum presented by the β-sheet is of lower intensity, showing a negative band close to 217 nm, a positive one close to 195 nm, and another negative band close to 180 nm (Brahms et al, 1977).
The lipocalins have characteristic structural elements showing approximately 7% of α-helices, 47% β-sheet and 45% randomized structures. (Flower, 1996). The circular dichroism spectrum of Lopap (
The native Lopap and the rLopap are able to activate prothrombin using preferentially the S-2238 substrate. However, in same concentrations, rLopap is less efficient (
The prothrombin (10 μM) was activated by rLOPAP (2 μM) in presence and absence of 5 μM phospholipids (phosphatidyl Serine:phosphatidyl Colina PS:PC), in reaction buffer (Tris-HCl 0.02M, NaCl 0.15M pH 8.0 with CaCl215 mM). Aliquots of 10 μl were collected in different times of the reaction (1 min; 1 h 30 m; 5 h and 18 h) for being analyzed in SDS-PAGEs 10% (
Under non-reduced conditions bands of 72 kDa (prothrombin), of 52 kDa probably corresponding to the prothrombin F1.2, one of 36 kDa corresponding to the thrombin or to the prethrombin 2, and one of 24 kDa corresponding to the fragment 1 (F1) of the prothrombin could be observed. Under reduced conditions, bands of 52 kDa (F1.2), 36 kDa (prethrombin 2), 32 (B chain of the prothrombin) and 27 kDa (F1) were observed.
For verifying the influence of the prothrombinase complex components in the prothrombin activation by r-LOPAP, the prothrombin (10 μM) was activated by r-LOPAP (2 μM) with PS:PC 5 mM in presence and in absence of the Va 200 μM Factor. The reaction buffer used was Tris-HCl 0.02M, NaCl 0.15M pH 8.0 with CaCl2 15 mM. The aliquots (10 μl) were collected in different times of incubation (1 min; 1 h 30 m; 5 h and 18 h) for being analyzed by SDS-PAGE (
Mice treated with rLopap intravenous administrations of 125, 250 and 500 μg/kg, considering the weight of the animal, were maintained alive and showed good life conditions after 48 hours of treatment. However blood showed unclotability and the plasmatic fibrinogen levels measured by the Clauss test were undetectable either after 2 and 48 hours after the rLopap administration (Table 1). Doses of 500 μg/kg did not show any toxic effect in the animals that continued without clear alterations, only presenting a longer time of coagulation period that lasted for at least 48 h.
Treatment with doses lower than 125 μg/kg can turn longer the coagulation time of the fibrinogen without provoking severe alterations in the microcirculation.
The capacity of the recombinant form of native Lopap, (rLopap) in activating prothrombin was indirectly determined through the thrombin formation essay when considering the prothrombin with the S-2238 chromogenic substrate. The prothrombin activator activity of the protein (15 nM) was evaluated after pre-incubation for 20 min at 37° C. with prothrombin (90 nM), in presence of CaCl2 5 mM for a final volume of 100 μl. This reaction occurred in Tris-HCl 50 mM, NaCl 100 mM, pH 8, 3, containing imidazol 150 mM. The hydrolysis of S-2238 40 μM by the thrombin formed by Lopap, using 90 nM of prothrombin was followed spectrophotometrically in 405 nm for 20 minutes at 37° C.
Aiming to verify whether rLopap can be used as a component of a diagnostic kit for prothrombin dosage, 50 μl of human plasma was diluted 1/40 in buffer TRIS-HCl 20 mM, NaCl 100 mM, pH 8.0, incubated 5 min at 37° C. with 15 μl of CaCl2 50 mM and 40 μl of rLopap for final concentration of 5 μg/ml. After that, 20 μl of S2238 substrate (Chromogenix) 3 mM was added to that and incubation was conducted for more 5 min at 37° C. The reaction was interrupted with 50 μl of acetic acid 30% and the substrate hydrolysis was measured spectrophotometrically in 405 nm.
The prothrombin concentration was calculated in accordance with a standard curve obtained from the dilutions of 1/30, 1/40, 1/80 and 1/160 (150, 100, 50 and 25% of activity respectively) of standard human plasma (Dade-Behring) prepared using the same procedures.
The prothrombin concentration in a human plasma sample showed 93% of activity. Controls available in the market (normal and pathologic-Dade-Behring) were used for validating this result. For the normal control (70-100% of activity) 86% was obtained as result and for the pathologic control (35%-50%) 41% of activity was reached. The prothrombin deficient plasma, used as control, showed a prothrombin concentration of 5%. These data indicate that rLopap can be used for determining prothrombin levels in plasmas of patient.
Positive clones with inserts amplified by primer 1.
The sequences were obtained in the “GenBank” data bank, showing similarities between Lopap and the proteins of the lipocalin family. (pfam00061) with Score=49.3 bits and E-value 2e-07. BBP—BILIN-BINDING PROTEIN, Pieris brassicae (gi 1705433); MUP—MAIN PRECURSOR OF THE URINARY PROTEIN, Rattus norvegicus (gi 127533); Prot-1—PROTEIN 1 OF THE VON EBNER'S GLAND, Rattus norvegicus (gi 12621114); ApoD PRECURSOR OF THE APOLIPOPROTEIN D, Homo sapiens (gi 4502163); INS-A —INSECTICYANIN A FORM Manduca sexta (gi 124151); CC-A2—SUB-UNITY A2 OF THE CRUSTACYANIN A2 Homarus gammarus (gi 117330); CC-C1.—SUB-UNITY C1 OF THE CRUSTACYANIN Homarus gammarus (gi 117420); PURP.—PRECURSOR OF THE PURPURIN Gallus gallus (gi 131549). High similarity represented in bold. The regions with high similarities with lipocalin characteristics are emphasized.
substrate in absence of FII and activators (white); ▪ FII control without activator; rLopap and Δ native Lopap.
MW Marker [Myosin (200 Kda), Phosphorylase B (97.4 KDa), BSA (67 KDa), Ovalbumine (43 KDa), Carbonic Anidrase (29 KDa), b-Lactoglobulin (18.4 KDa), Lysozyme (14.3 KDa); Prothrombin (PT);
MW Marker [Myosin (200 Kda), Phosphorylase B (97.4 KDa), BSA (67 KDa), Ovalbumine (43 KDa), Carbonic anidrase (29 KDa), b-Lactoglobulin (18.4 KDa), Lysosima (14.3 KDa);
1) Prothrombin (PT); 2) PT+LOPAP+PS:PC+Va (1 min inc); 3) PT+LOPAP+PS:PC+Va (90 min inc); 4) PT+LOPAP+PS:PC+Va (5 h inc); 5) PT+LOPAP+PS:PC+Va (18 h inc); 6) Thrombin, 7) Prothrombin (PT); 8) PT+LOPAP+PS:PC (1 min inc); 9) PT+LOPAP+PS:PC (90 min inc); 10) PT+LOPAP+PS:PC (5 h inc); 11) PT+LOPAP+PS:PC (18 h inc); 12) Thrombin
| Number | Date | Country | Kind |
|---|---|---|---|
| PI0403882-7 | Aug 2004 | BR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/BR05/00171 | 8/24/2005 | WO | 00 | 4/11/2008 |
