Patent Application
20100261213
The present invention relates to protein tyrosine phosphatase (PTP) and a method for preparing the same.
Protein tyrosine phosphorylation-dephosphorylation plays a very important role in intracellular signal transduction system. In particular, protein tyrosine phosphorylation-dephosphorylation is involved in changes of cells such as responses to foreign stimuli, cell growth, differentiation and apoptosis, etc. Therefore, protein tyrosine kinase (PTK; Curr Pharm Des 13:2751-65, 2007; Curr Med Chem 14:2214-34, 2007) and protein tyrosine phosphatase (PTP) are important target proteins for the treatment of such diseases accompanying the change of cells as cancer, vascular disease, immune disease and nervous disease (Curr Cancer Drug Targets 6:519-532, 2006; Med Res Rev 27:553-73, 2007). Glivec, the inhibitor of abl-PTK which is one of PTKs, draws our attention as a novel drug for the treatment of chronic myeloid leukemia (Curr Opin Drug Discov Devel 7:639-48, 2004). Unlike PTK, PTP has not been explored much. But, some of PTPs are now targets of studies to treat cancer and diabetes, suggesting that PTPs have a great potential as a target protein for the treatment of such diseases.
Destruction of intracellular signal transduction system easily results in the development of a disease. So, it has been reported that PTPs have something to do with diseases and thus some of PTPs have been targets for the development of a novel drug. Humans have approximately 100 types of PTPs (Cell 117:699-711, 2004). Among these PTPs, approximately 20 PTPs have been used as a target for the development of a novel drug since their involvement in diseases was confirmed. It is thereby presumed that the remaining 80 PTPs might be involved in disease development. To develop an effective novel drug, activity of a target PTP has to be inhibited without affecting other PTPs. However, active sites of PTPs are all similar in their structures, so that a compound capable of inhibiting activity of a target PTP could inhibit activities of other PTPs. If that is the case, intracellular signal transduction network can be disturbed randomly with causing side effects with a used drug. In particular, risks of using PTPs whose intracellular functions have not been disclosed are especially great.
Therefore, it is important to develop PTP inhibitor to investigate all the activities of every PTP so as to screen a specific PTP specific compound. But, this is only possible when active protein of each PTP is identified. This active protein of each PTP is also necessary for the studies on cell functions in PTP related disease or for the development of an antibody for diagnosis of a disease. In order to use PTP for the above purposes, it is required for PTP to maintain its activity for a long time as stable as possible, and it is advantageous for PTP not to be fused with a fusion protein such as MBP and GST for the construction of an effective antibody.
Research groups have succeeded in expressing active domains sporadically and studied on the structures and functions of those active domains, which were not enough, though, and only about 20 reports have been made so far which still leave questions in activity and stability. Large scale expression of above approximately 100 PTP proteins has not been successful and the expression of 77 PTP proteins in E. coli using MBP fusion protein was successfully induced first by the present inventors (Korean Patent No. 746993). However, the use of MBP fusion protein has a problem, which is the decrease of stability after MBP elimination. So, MBP is limited in use for measuring activity level for the development of an inhibitor or for the construction of a selective antibody.
The present inventors precisely predicted N-terminal and C-terminal of PTP active domain, by taking advantage of protein structure prediction method using a computer. And the present inventors further completed this invention by confirming that 60 PTP active domains could be expressed stably without using a fusion protein only by cloning and expressing the active domains.
It is an object of the present invention to provide a method for preparing a recombinant PTP active domain.
It is another object of the present invention to provide a recombinant PTP active domain prepared by the method of the present invention.
It is also an object of the present invention to provide a polynucleotide encoding the above recombinant PTP active domain.
It is further an object of the present invention to provide an expression vector containing the said polynucleotide.
It is also an object of the present invention to provide a transformant transfected with the said expression vector.
It is also an object of the present invention to provide a kit for screening PTP inhibitor or activator containing the said recombinant PTP active domain.
It is also an object of the present invention to provide PTP specific antibody capable of binding specifically using the said recombinant PTP active domain.
It is also an object of the present invention to provide a method for screening PTP activity inhibitor or activator using the said recombinant PTP active domain.
It is also an object of the present invention to provide a method and kit for measuring level of PTP using the said recombinant PTP active domain.
To achieve the above objects, the present invention provides a method for preparing a recombinant PTP active domain comprising the following steps:
1) investigating homology among sub-groups of protein tyrosine phosphatase (PTP) and selecting the region exhibiting high homology;
2) examining whether the selected region of step 1) corresponds to the active domain of the standard protein whose secondary and tertiary structures have already been identified;
3) analyzing the secondary structure of the selected region of step 1) if it corresponds to the active domain and then primary determining the boundary of PTP active domain by the location not containing helix or sheet of the secondary structure;
4) secondary determining the boundary both N-terminal and C-terminal of the PTP active domain primarily determined in step 3) to be a soluble form by amino acid analysis;
5) constructing an expression vector containing a polynucleotide encoding the amino acids included in the inside of the boundary of the PTP active domain secondarily determined in step 4);
6) generating a transformant by introducing the expression vector of step 5) into a host cell; and,
7) inducing expression of the recombinant PTP active domain by culturing the transformant of step 6) and recovering thereof.
The present invention also provides a recombinant PTP active domain prepared by the method of the present invention.
The present invention further provides a polynucleotide encoding the said recombinant PTP active domain.
The present invention also provides an expression vector containing the said polynucleotide.
The present invention also provides a transformant transfected with the said expression vector.
The present invention also provides a kit for screening PTP inhibitor or activator containing the said recombinant PTP active domain.
The present invention also provides PTP specific antibody capable of binding specifically using the said recombinant PTP active domain.
The present invention also provides a method for screening PTP activity inhibitor or activator comprising the following steps:
1) treating PTP specific substrate and candidates to the PTP active domain, followed by determining activity based on optical density after measuring the optical density; and,
2) selecting candidates which reduce or increase the activity of the recombinant PTP active domain by comparing the activity of step 1) with that of the non-treated control.
The present invention also provides a method for measuring level of PTP comprising the following steps:
1) adding the PTP specific antibody of the present invention to the sample separated from a subject to conjugate PTP in samples with the antibody; and,
2) measuring a level of PTP conjugated with the antibody of step 1).
The present invention also provides a kit for measuring level of PTP which contains the PTP specific antibody of the present invention.
The present invention also provides a use of the said recombinant PTP active domain for the screening of PTP activity inhibitor or activator.
In addition, the present invention provides a use of the said PTP specific antibody for the measurement of PTP level in sample.
As explained hereinbefore, PTP prepared by the method of the present invention can be effectively used as a protein for high efficiency drug screening for the development of a novel drug, as an antigen protein for the construction of a selective antibody and as a protein for the studies of PTP structure and functions.
The application of the preferred embodiments of the present invention is best understood with reference to the accompanying drawings, wherein:
Lane 1: T38 not treated with protease; and,
Lane 2-Lane 13: T38 treated with protease with increasing the concentration.
a: solubility and stability of full length pk7; and,
(lanes 1, 3, 4 and 6: standard lanes [for pk7 location identification]; lanes 2 and 5: supernatant after cell lysis)
b: solubility and stability of redesigned pk7 domain
(lanes 1, 3, 5, 6 and 8: standard lanes; lane 2: marker; lanes 4 and 7: supernatant after cell lysis).
The terms used in this invention are described hereinafter.
“PTP active domain” indicates not full length PTP protein but a functional fragment thereof determined by the method of the present invention.
Hereinafter, the present invention is described in detail.
The present invention provides a method for preparing a recombinant PTP active domain comprising the following steps:
1) investigating homology among sub-groups of protein tyrosine phosphatase (PTP) and selecting the region exhibiting high homology;
2) examining whether the selected region of step 1) corresponds to the active domain of the standard protein whose secondary and tertiary structures have already been identified;
3) analyzing the secondary structure of the selected region of step 1) if it corresponds to the active domain and then primary determining the boundary of PTP active domain by the location not containing helix or sheet of the secondary structure;
4) secondary determining the boundary both N-terminal and C-terminal of the PTP active domain primarily determined in step 3) to be a soluble form by amino acid analysis;
5) constructing an expression vector containing a polynucleotide encoding the amino acids included in the inside of the boundary of the PTP active domain secondarily determined in step 4);
6) generating a transformant by introducing the expression vector of step 5) into a host cell; and,
7) inducing expression of the recombinant PTP active domain by culturing the transformant of step 6) and recovering thereof.
The representative tertiary structure of PTP active domain (PTP1B) is presented in
The investigation of homology in step 1) can be performed by computer programs such as ClustalX, KALIGN (At Karolinska Institute or at EB), MAFFT (At Kyushu University, EBI or at MyHits) and Muscle (At Berkeley or at BioAssist). The sub-groups of step 1) are classified into 5 groups: receptor, non-receptor, MKP (Mitogen-Activated protein Kinase phosphatase), DUSP (Dual-specificity phosphatases) and CDCl4 (Cell division cycle 14) homologue. These 5 groups are composed of those PTPs having similar amino acid sequences and active domain structures. Therefore, based on the tertiary structures in each group of PTPs which were already identified, it was possible to predict secondary and tertiary structures of other PTPs in the same group. The identified tertiary structure in each group and PDB (Protein Data Bank) accession codes are as follows: receptor: RPTPα (1YFO) and LAR (1LAR); non-receptor: PTP1B (2HNQ) and TCPTP (1L8K); MKP: PYST1 (1MKP); DUSP: VHR (1VHR); CDC14: CDC14B (1FPZ)
The analysis of the secondary structure in step 2) can be performed by computer programs such as GOR IV SECONDARY STRUCTURE PREDICTION METHOD (//pbil.ibcp.fr/), PHDsec (//www.predictprotein.org/) and Jpred (//www.compbio.dundee.ac.uk/jpred), etc.
The boundary both N-terminal and C-terminal in step 4) is preferably determined for N-terminal and C-terminal of PTP active domain to have at least 2-3 soluble amino acids and for the start and end regions where protein folding occur to be exposed on the surface and for its secondary structure not to contain helix or sheet. The soluble amino acids herein are the amino acids having electric charge or small amino acids. The small amino acid herein is exemplified by serine or glycine. The amino acid having electric charge is exemplified by lysine, arginine, glutamine, asparagine, glutamic acid and aspartic acid.
If N-terminal and C-terminal of a recombinant protein are soluble, these terminals are easily exposed on water-soluble condition, which means these terminals can be stably expressed in an aqueous solution, and if helix or sheet structure which plays an important role in protein folding is located in the terminal of a domain, protein folding is not completed successfully and thus it is very difficult to be expressed stably in an aqueous solution.
The present inventors analyzed hydrophobic properties and secondary structure constitutions of amino acids by using ProtScale (//www.expasy.org/tools/protscale.html) of ExPASy server (Swiss Institute of Bioinformatics) (see
In the step of determining boundary of the active domain, an additional step of re-designing the boundary of PTP active domain may be included by treating protease, if the activity and stability of a recombinant PTP active domain are very low (see
The expression vector containing a polynucleotide encoding amino acids included in the boundary of PTP active domain of step 3) is as shown in
In step 5), a recombinant PTP active domain was obtained under the controlled oxidation-reduction condition. In a preferred embodiment of the present invention, oxidation-reduction condition was maintained by using 5-20 mM of DTT or beta-mercaptoethanol. Approximately 30 PTP active domains were stably expressed and purified, followed by SDS-PAGE to investigate the purity of the proteins (see
The present invention also provides a recombinant PTP active domain prepared by the method of the present invention.
The PTP active domain of the present invention has high activity and stability (see
The present invention further provides a polynucleotide encoding the said recombinant PTP active domain.
The present invention also provides an expression vector containing the said polynucleotide.
The vector contains the said polynucleotide in its backbone structure. The backbone vector of the present invention is preferably the vector contains restriction enzyme sites in multiple cloning sites which are generally not included in the polynucleotide encoding each polypeptide in the boundary of PTP active domains represented by SEQ. ID. NO: 113-SEQ. ID. NO: 168 and SEQ. ID. NO: 169-SEQ. ID. NO: 177, but not always limited thereto. The vector herein can be selected among various vectors capable of transfecting E. coli, such as pT7, pET/Rb, pGEX, pET28a, pET-22b(+) and pGEX. In a preferred embodiment of the present invention, polynucleotides encoding polypeptides in the boundary of PTP active domains represented by SEQ. ID. NO: 113-SEQ. ID. NO: 168 were introduced into pET28a vector (see
The present invention also provides a transformant transfected with the said expression vector.
The transformant herein can be effectively used for large scale preparation of PTP active domain facilitating disease diagnosis and studies of various cell functions.
The present invention also provides a kit for screening PTP inhibitor or activator containing the said recombinant PTP active domain.
The recombinant PTP active domain can be fixed on a solid carrier. The kit can additionally include a substrate for the measurement of PTP active domain activity, a reaction buffer and a reaction termination reagent, etc. The substrate herein is exemplified by DiFMUP (6,8-difluoro-4-methylumbelliferyl phosphate), OMFP (3-O-methylfluoresceinphosphate) and PTP substrate peptide labeled with fluorescent material. In a preferred embodiment of the present invention, DiFMUP was used as a substrate.
The present invention also provides PTP specific antibody capable of binding specifically using the said recombinant PTP active domain.
The antibody of the present invention can be a monoclonal antibody or polyclonal antibody. The antibody herein can be easily prepared by using the said recombinant PTP active domain of the present invention as an antigen according to the conventional antibody preparation method.
The antibody includes a polyclonal antibody, a monoclonal antibody and a fragment capable of binding to epitope.
A polyclonal antibody can be prepared as follows; one of the said recombinant PTP active domains is injected into a test animal; blood sample is taken from the animal; and then serum containing antibody is separated to isolate the antibody. Such polyclonal antibody can be purified by any methods known to those in the art and can be produced from host animals which are exemplified by goat, rabbit, sheep, monkey, horse, pig, cow, dog, etc.
A monoclonal antibody can be prepared by any method that facilitates the production of antibody molecules via culturing the continuous cell line. The method is exemplified by hybridoma technique, human-B-cell hybridoma technique, and EBV-hybridoma technique, but not always limited thereto (Kohler G et al., Nature 256:495-497, 1975; Kozbor D et al., J Immunol Methods 81:31-42, 1985; Cote R J et al., Proc Natl Acad Sci 80:2026-2030, 1983; Cole S P et al., Mol Cell Biol 62:109-120, 1984).
An antibody fragment containing a specific binding site for one of the said recombinant PTP active domains can be prepared. For example, F(ab′)2 fragment can be prepared by fractionation of an antibody molecule by using pepsin and Fab fragment can be prepared by reducing disulfide bridge of F(ab′)2 fragment, but not always limited thereto. Alternatively it is also possible to identify a monoclonal Fab fragment having desired specificity by constructing Fab expression library (Huse W D et al., Science 254: 1275-1281, 1989).
The present invention also provides a method for screening PTP activity inhibitor or activator comprising the following steps:
1) treating PTP specific substrate and candidates to the PTP active domain, followed by determining activity based on optical density after measuring the optical density; and,
2) selecting candidates which reduce or increase the activity of the recombinant PTP active domain by comparing the activity of step 1) with that of the non-treated control.
The candidate of step 1) can be selected from the group consisting of natural compounds, synthetic compounds, RNA, DNA, polypeptides, enzymes, proteins, ligands, antibodies, antigens, metabolites of bacteria and fungi and bioactive molecules, but not always limited thereto.
The present invention also provides a method for measuring level of PTP comprising the following steps:
1) adding the PTP specific antibody of the present invention to the sample separated from a subject to conjugate PTP in samples with the antibody; and,
2) measuring a level of PTP conjugated with the antibody of step 1).
In step 1), the sample can be selected from the group consisting of blood, tissues and exudates. In step 2), the measurement is performed by a method selected from the group consisting of Western blotting, ELISA (enzyme-linked immunosorbent assay), colorimetric method, electrochemical method, fluorimetric method, luminometry, particle counting method, visual assessment and scintillation counting method.
The present invention also provides a kit for measuring level of PTP which contains the PTP specific antibody of the present invention.
The antibody herein can be fixed on a solid substrate for the convenience in washing, separation of a complex and the following steps. The solid substrate is exemplified by synthetic resin, nitrocellulose, glass plate, metal plate, microsphere and microbead, etc. The synthetic resin herein is exemplified by polyester, polyvinyl chloride, polystyrene, polypropylene, PVDF and nylon.
To mix the sample separated from a subject with the PTP specific antibody of the present invention, the sample can be diluted before the mixing. The sample can be pre-treated in order to increase PTP sensitivity by anion exchange chromatography, affinity chromatography, size exclusion chromatography, liquid chromatography, sequential extraction or gel electrophoresis, etc, but not always limited thereto.
The kit of the present invention can contain a ligand suitable for conjugating PTP specific antibody. The ligand herein is preferably secondary antibody which is specific for protein A or antibody for detection. The PTP specific antibody and ligand of the present invention can be conjugates labeled with coloring enzyme, fluorescein, isotope or colloid as probe for detection. The PTP specific antibody is preferably treated by biotinylation or with digoxigenin to be conjugated with the ligand, but the treatment method is not limited thereto. The ligand is preferably treated with streptavidin or avidin to be conjugated with PTP specific antibody, but not always limited thereto.
The kit for measuring the level of PTP active domain of the present invention is designed to screen the amount of PTP specific antibody and PTP specific antibody in the PTP complex in the sample. The kit is also capable of measuring the level of PTP by screening the ligand treated with the said antibody and PTP complex in the sample. The measurement or detection of PTP specific antibody and ligand is performed by fluorescence, iluminescence, chemiluminescence, optical density, reflection or transmission.
To screen the PTP specific antibody or ligand, high throughout screening (HTS) system is preferably used. At this time, fluorescence assay detecting fluorescence with fluorescent material labeling as probe for detection; radio assay detecting radioactive rays with isotope labeling as the probe; SPR (surface plasmon resonance) method measuring real time changes of Plasmon resonance on the surface without labeling; or SPRI (surface plasmon resonance imaging) method is used, but not always limited thereto.
For the fluorescence assay, an antibody for detection is labeled with a fluorescent material and then spotted, and signal is detected by fluorescent scanner program. The fluorescent material herein is preferably selected from the group consisting of Cy3, Cy5, poly L-lysine-fluorescein isothiocyanate (FITC), rhodamine-B-isothiocyanate (RITC) and rhodamine, but not always limited thereto. The SPR system facilitates real-time analysis of level of an antibody conjugation without fluorescent material labeling. But, it cannot facilitate simultaneous analysis of different samples. The SPRI can be used for simultaneous analysis of different samples but sensitivity is low.
The present invention also provides a use of the said recombinant PTP active domain for the screening of PTP activity inhibitor or activator.
In addition, the present invention provides a use of the said PTP specific antibody for the measurement of PTP level in sample.
The sample is tissues or body fluids including blood, urine and tear.
Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples.
However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.
PTP active domains are classified into 5 groups: receptor, non-receptor, MKP (map kinase phosphatase), DUSP (dual-specificity phosphatases) and CDC14 (cell division cycle 14) homologue, followed by comparison of their amino acid sequences. The structures of these 5 groups were predicted based on the homology of their amino acid sequences, which were used for dividing PTP subgroups (Alonso et al., Cell 117:699-711, 2004). Based on the tertiary structures already identified [receptor: RPTPa (1YFO); non-receptor: PTP1B (2HNQ) and TCPTP (1L8K); MKP: PYST1 (1MKP); DUSP: VHR (1VHR); CDC14: CDC14B (1FPZ)], amino acid sequences of each group were arranged by using Clustal X program (
At the same tine, the secondary structure was predicted by using GOR IV SECONDARY STRUCTURE PREDICTION METHOD (//pbil.ibcp.fr/).
For the stable expression in aqueous solution, it is preferred for N-terminal and C-terminal of a protein to be composed of water-soluble amino acids. So, hydrophobicity and secondary structure of the amino acid were analyzed by using ProtScale (//www.expasy.org/tools/protscale.html) of ExPASy server (Swiss Institute of Bioinformatics). For example, based on the prediction of hydrophilic/hydrophobic region of the amino acid sequence of MKP3(pk9) by ExPASy server, the boundary of hydrophilicity (
Based on the above prediction, 1-52 amino acid sequences with modified boundary to increase solubility were obtained.
After cloning the PTP active domain determined in Example <1-2>, it was expressed in E. coli and purified therefrom. After storing for a while, a proper amount of protein solution was ultra-centrifuged to separate supernatant and precipitate. SDS-PAGE was performed with the precipitate by the same manner as described in Example 3 to investigate whether the precipitate contained the target protein, leading to the examination of solubility.
Based on the result of Example <1-3-1>, 20 μg of PTP active domain having low solubility and stability was serially diluted from 1:1 to 1:1,000, followed by reaction with trypsin (Sigma, USA) or chymotrypsin (Sigma, USA) at 37° C. for 30 minutes. SDS-PAGE was performed by the same manner as described in Example 3 to confirm digestion.
As a result, it was confirmed that stability of T38 was maintained even with the increase of protease concentration (
The stable PTP active domain obtained in Example <1-3-2> was modified and reformed by N-terminal sequencing and mass spectrometry.
The protein band cut by protease obtained in Example <1-3-2> was transferred to PVDF membrane. The band was cut and treated with a reagent recognizing and digesting N-terminal, followed by HPLC stepwise to arrange amino acids. Mass spectrometry was performed with the band to calculate the mass exactly and select stable domains. The re-designed domains were tested for activity and stability by the same manner as described in Example 4.
As a result, as shown in
Expression vectors capable of expressing 1-56 PTP active domains determined in Example 1 without help of a fusion protein were constructed.
The multiple cloning sites of PET28a (Novagen, USA) contains those restriction enzyme sites not included in DNA sequences of PTP active domains (SEQ. ID. NO: 113-SEQ. ID. NO: 168) most, so that it was used as a backbone vector of the present invention. As shown in Table 2, to amplify DNA sequences of PTP active domains 1-56 represented by SEQ. ID. NO: 113-SEQ. ID. NO: 168, PCR was performed with primers represented by SEQ. ID. NO: 1-SEQ. ID. NO: 112 using cDNA libraries of brain, muscle and testis purchased from Clontech as template DNAs as follows; at 95° C. for 5 minutes, at 95° C. for 1 minute, at 55-60° C. for 1 minute, at 72° C. for 90 seconds (30 cycles) and at 72° C. for 10 minutes. The amplified PCR products were digested with NdeI, EcoRI or BamHI, which were inserted into pET28a vector (Novagen, USA) and then named respectively pET28a-PTP 1-56 (
<2-2> Conditions for Large Scale Expression with Maintaining Activity and Stability
E. coli was transfected respectively with the 56 vectors constructed in Example <2-1> according to the method of Hanahan (Hanahan D, DNA Cloning vol. 1 109-135, IRS press 1985).
Particularly, E. coli BL21-DE3-RIL treated with CaCl2 was transfected with vectors constructed in Example <2-1> by heat-shock method. Then, the cells were cultured in medium containing kanamycin (Sigma, USA). Colonies having kanamycin resistance were selected. These colonies were cultured in LB medium for overnight and then some of the seed culture solution was inoculated in LB medium containing 30 μg/ml of kanamycin, followed by culture until stationary phase. The culture solution was diluted at the ratio of 1:100 and inoculated in fresh LB medium (400 ml/flask). Temperature was lowered slowly from 37° C. to 17° C. during 2-3 hour culture. Then, culture was continued at 17° C. at 200 rpm. When OD600 of the culture solution reached 0.5, IPTG was added at the lowest concentration (0.05-0.1 mM), followed by further culture for 20 or 16-18 hours to induce expression of PTP active domain.
<2-3> Conditions for Purification and Storage with Maintaining Activity and Stability
E. coli cultured in Example <2-2> was centrifuged at 4° C. at 6,000 rpm for 5 minutes. The cell precipitate was recovered, which was resuspended in 5 ml of cell lysis buffer (10 mM Tris-HCl buffer, pH 7.5, 10 mM EDTA). The cells were lysed using ultrasonicator at 4° C. Centrifugation was performed at 4° C. at 13,000 rpm for 10 minutes to separate supernatant and insoluble aggregate. Protein was eluted from the supernatant by linear density gradient using Ni-NTA resin (Qiagen, USA) at 4° C. for about 3 hours from low concentration buffer [20 mM Tris-HCl buffer, pH 7.5, 0.2 M NaCl, 1.0 mM PMSF, 4 mM β-mercaptoethanol (Sigma, USA)] to high concentration buffer [0.5 M imidazole (Sigma, USA) was added to the low concentration buffer]. The histidine tag of N-terminal of the eluted protein was eliminated by treating thrombin (protease) (Sigma, USA) by 1 unit/100 μg protein. The protein was purified by ion exchange chromatography (GE Healthcare, USA) and gel filtration chromatography (GE Healthcare, USA). During the purification of PTP active domain, 10 mM β-mercaptoethanol (Sigma, USA) or DTT (Promega, USA) was added to the buffer and pH of the buffer was regulated to 6.5-8.0. The purified PTP active domain was stored at 4° C. with the addition of 10% glycerol in protein solution [10% glycerol solution prepared by adding 100-250 mM NaCl, 10 mM reducing agent (β-mercaptoethanol or DTT) and 0.5˜2 μg/ml protease inhibitor (Sigma, USA) to pH 7.5-8.0 Tris buffer].
The results (size and purity of protein) of purification of PTP active domain obtained in Example 2 were confirmed by SDS-PAGE.
The concentration of PTP active domain obtained by the method of Example 2 was measured by using Bio-Rad protein assay kit. The protein was mixed with 5×SDS (0.156 M Tris-HCl, pH 6.8, 2.5% SDS, 37.5% glycerol, 37.5 mM DTT) at the ratio of 1:4, followed by boiling at 100° C. for 10 minutes. 1-2 μg of the boiled sample was loaded in each well of 10% SDS-PAGE gel, followed by developing at 125 V for 2 hours. After Coomassie staining, destaining was performed and expression of each recombinant protein was examined.
As a result, as shown in
The activity of PTP active domain obtained in Example 2 was measured by using DIFMUP (Molecular probe, USA).
10 mM DiFMUP (Molecular probe, USA) suspension was diluted with reaction buffer (20 mM Tris-HCl, pH8.0, 0.01% Triton X-100, 5 mM DTT; Sigma, USA). 10 μM of the substrate (final concentrations are shown in Table 3) was reacted with the PTP active domain obtained in Example 2 at room temperature for 90 minutes. The reaction was terminated by adding 1 mM sodium orthovanadate (Sigma, USA). Relative fluorescence unit (RFU) was calculated by measuring OD355/460 with victor21420 multilabel counter plate reader (Perkin Elmer, USA) at a regular time interval for 90 minute reaction. The value was compared with that of substrate alone to evaluate the activity.
As a result, as shown in reaction saturation curve in
<4-2> Evaluation of Activity after Storing at Room Temperature and at Low Temperature
The stability of the PTP active domain obtained in Example 2 was measured.
PTP active domain was stored at different temperatures including room temperature and low temperature (4° C.) and at different concentrations and for different periods of time, and then the activity was measured by the same manner as described in Example <4-1>, which was compared with that measured in Example <4-1>. The concentration of the reactant protein and reaction time varies from a substrate, but generally the concentration of the protein herein was determined as much as all substrates were not turned into reactants, and as shown in
As a result, the activity was maintained for approximately 6 hours at room temperature. When the domain was stored at a low temperature at the concentration of 0.5˜1.0 mg/ml, the activity was maintained for about 2 weeks.
Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-125162 | Dec 2007 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR08/04524 | 8/4/2008 | WO | 00 | 6/4/2010 |
