Eukaryotic expression, purification and activity characterization of human soluble DSG2 extracellular domain protein

Objective:To construct a secretory eukaryotic expression vector of DSG2 fused with the Fc region of the human IgG,to validate its expression in 293T cells,and to purify the secretory protein with biological activity.Methods:The DSG2 extracellular domain fragment gene(DSG2ex),was amplified by PCR,and was inserted into the eukaryotic expression plasmid pCMV3-IgG1 to construct the recombinant eukaryotic expression plasmid-pCMV3-DSG2ex-IgG1.The successfully constructed eukaryotic expression plasmid was transfected into 293T cells to express and secrete DSG2 extracellular domain protein.The targeted protein was purified from the cell culture supernatant by Protein A affinity chromatography and confirmed by Western Blotting and ELISA.Results:The pCMV3-DSG2ex-IgG1 eukaryotic expression plasmid was successfully constructed.The highest protein expression level was obtained with 293T cells after 96 h of transfection.The relative molecular mass of the purified product was between 100 and 130 kDa was estimated by SDS-PAGE,which was consistent with the expectation.The yield of the purified protein reached 0.8 mg/ml with a purity over 90%.The purified DSG2 extracellular domain protein with IgG1 tag was recognized by IgG monoclonal antibodies by Western blotting.Moreover,the ELISA results showed that the prepared DSG2 extracellular domain protein had significant binding activity to human type 55 adenovirus Fiber Knob protein(HAdV-55).Conclusion:A simple and efficient method for eukaryotic expression and purification of human soluble DSG2 extracellular domain protein was successfully established,and biologically active DSG2 extracellular domain protein was purified,which laid the foundation for the later study of its protein function and anti-adenovirus drugs.

Purification and enzymatic properties of arsenic resistance protein ArsH from heterogeneous expression in E.coli BL21

Four arsenic-resistance genes(arsB,arsC,arsH,arsR) have been discovered in Acidithiobacillus ferrooxidans.Their gene sequences have been identified and three different arsenic-resistance mechanisms have been elucidated.However,the function of the arsH gene in At.ferrooxidans remains unclear.In order to evaluate the function of the arsH gene,we cloned it and expressed it in Escherichia coli.The protein was purified and its relative molecular mass was determined by SDS-PAGE(Sodium dodecyl sulfate-polyacrylamide gel electrophoresis).The results indicated that the relative molecular mass of the purified ArsH was approximately 29 kDa.The purified protein ArsH from E.coli BL21 was a flavoprotein that oxidized in vitro NADPH with an optimal pH of 6.4.

Expression,purification and immunocharacteristics of recombination UreB protein of H.pylori

INTRODUCTIONHelicobacter pylori (H . pylori) is associated with the development of chronic gastritis ,peptic ulcer and gastric cancer and gastric MALT lymphoma[1-9],H .pylori has many antigens ,including urease ,heat shock protein and vacuolating cytotoxin and so on ,and urease is an important factor in the colinization of the gastric mucosa and suspected to cause damage to the gastric mucosa[10-14].At the same time ,urdase is also one of the important protective antigens .

Expression and Purification of Enterovirus Type 71 Polyprotein P1 using Pichia pastoris system

Enterovirus type 71（EV71） causes severe hand-foot-and-mouth disease （HFMD） resulting in hundreds of deaths of children every year; However, currently, there is no effective treatment for EV71. In this study, the EV71 poly-protein （EV71-P1 protein） gene was processed and cloned into the eukaryotic expression vector pPIC9k and then expressed in Pichia pastoris strain GSll5. The EV71 P1 protein with a molecular weight of 100 kD was produced and secreted into the medium. The soluble EV71 P1 protein was purified by column chromatography with a recovery efficiency of 70%. The result of the immunological analysis showed that the EV71 P1 protein had excellent immunogenicity and could stimulate the production of EV71-VP1 IgG antibody in injected rabbits. We suggest that EV71-P1 protein is an ideal candidate for an EV71 vaccine to prevent EV71 infection.

Synthesis,Expression and Purification of S1 and S2 Fragments of SARS S Protein in E.coli

[Objective] To obtain pure recombinant S1 and S2 of SARS S protein. [Method] Using asymmetric PCR and ligation with endonuclease, S1 and S2 fragments of SARSV HK strain S gene were synthesized. Then, these two fragments were inserted into plasmid pET28a to obtain recombinant vectors pET28a-S1 and pET28a-S2, respectively. These recombinant vectors were transformed into E. coli BL21, and expression of S1 and S2 fragments were induced by IPTG. The conditions of expression and purification were optimized. [Result] The S1 and S2 fragments were amplified and successfully expressed in E. coli. [Conclusion] This research provides detection antigens for follow-up development of SARS vaccine.

Expression and Purification of SARS Coronavirus Membrane Protein

To construct a recombinant plasmid Pet23a-M, the gene encoding severe acute respiratory syndrome (SARS) coronavirus membrane protein was amplified by RT-PCR and cloned into the expression plasmid Pet23a. Results of restriction endonuclease analysis, PCR detection and DNA sequencing analysis revealed that the cloned DNA sequence was the same as that reported. The recombinants were transformed into Escherichia coli (E.Coli) BL21 (DE3) and induced by Isopropyl-β-D-thiogalactopyranoside (IPTG). The expression of 27 kD (1 kD=0.9921 ku) protein was detected by SDS-PAGE and pured by metal chelated chromatography. Results of Western-blot showed that this expressed protein could react with antibodies in sera of SARS patients during convalescence. This provided the basis for the further study on SARS virus vaccine and diagnostic agents.

Expression,Purification and Activity Detection of Structural Protein VP1 of Foot-and-Mouth Disease Virus Serotype A

The paper was to obtain the VP1 protein of FMDV serotype A with high activity. With recombinant plasmid pMD19A-T-vp1 as the tem- plate, vpl gene fragment amplified by PCR was connected into prokaryotic expression vector pET28a to construct recombinant plasmid pET-A-vpl. The E. coli BL21 （DE3） strain containing recombinant plasmid pET-A-vpl were induced by IPTG. SDS-PAGE showed that VP1 protein was ex- pressed in the form of inclusion body, and its molecular weight was about 29 ku. Based on the optimizing IPTG concentration and expression time, the largest expression of VP1 protein was induced by 0.3 mmol/L IPTG for 6 h at 37 ℃. Western-Blot analysis indicated that the expression of VP1 protein could be specifically recognized by positive serum of FMDV serotype A. ELISA test showed that VP1 inclusion body protein had high activity after purification by washing and renaturation by urea concentration gradient dialysis.

Development and Applications of a Calmodulin-Based Fusion Protein System for the Expression and Purification of WW and Zinc Finger Modules

Calmodulin from Homo sapiens is an α-helical calcium-binding protein that expresses to high levels in E. coli. When the N-terminus of a calmodulin variant is bound to Ca2+, it undergoes a conformational change, exposing hydrophobic pockets. This property can be utilized for purification purposes, as these pockets bind to phenyl sepharose resin with high affinity. Washing with EDTA chelates the Ca2+ ions from the protein, inducing a conformational change back to the more folded state and eluting the protein from the column. We describe herein the use of a protein expression and purification technique using the calmodulin variant and a short linker for proteolytic cleavage by the mutant NIa-Pro tobacco etch virus protease. We have shown this approach to be useful in obtaining purified quantities of various small proteins that could not be expressed using other methods, including high enough concentrations of a designed WW domain protein for NMR structural analysis. We have also obtained promising results on the usefulness of this procedure to express and purify zinc finger proteins without the addition of zinc ions or other cofactors.

Expression,Purification and Activity Detection of VP1 of A-type FMDV

[Objective] The research aimed to induce the expression of FMDV structural protein VP1 in E.coli and purify the protein,then detect the activity.[Method] The fragment coding VP1 was amplified by PCR and doubly digested with BamH Ⅰ and XhoⅠ,then cloned into expression vector pGEX-4T-1 and pPROExHTb respectively to get recombinant plasmid pGEX-4T-1-VP1 and pPROExHTb-VP1.The recombinant plasmid pGEX-4T-1-VP1 and pPROExHTb-VP1 was transformed into E.coli BL21(DE3)and induced by IPTG,fusion protein was identifie...

Prokaryotical expression of structural and non-structural proteins of hepatitis G virus

AIM: To study the epitope distribution of hepatitis G virus (HGV) and to seek for the potential recombinant antigens for the development of HGV diagnostic reagents. METHODS: Fourteen clones encompassing HGV gene fragments from core to NS3 and NS5 were constructed using prokaryotic expression vector pRSET and (or) pGEX, and expressed in E.coli. Western blotting and ELISA were used to detect the immunoreactivity of these recombinant proteins. RESULTS: One clone with HGV fragment from core to E1 (G1), one from E2 (G31), three from NS3 (G6, G61, G7), one from NS5B (G821) and one chimeric fragment from NS3 and NS5B (G61-821) could be expressed well and showed obvious immunoreactivity by Western blotting. One clone with HGV framment from NS5B (G82) was also well expressed, but could not show immunoreactivity by Western blotting. No obvious expression was found in the other six clones. All the expressed recombinant proteins were in inclusion body form, except the protein G61 which could be expressed in soluble form. Further purified recombinant proteins G1, G31, G61, G821 and G61-821 were detected in indirected ELISA as coating antigen respectively. Only recombinant G1 could still show immunoreactivity, and the other four recombinant proteins failed to react to the HGV antibody positive sera. Western blotting results indicated that the immunoactivity of these four recombinant proteins were lost during purification. CONCLUSION: Core to E1, E2, NS3 and NS5 fragment of HGV contain antigenic epitopes, which could be produced in prokaryotically expressed recombinant proteins. A high-yield recombinant protein (G1) located in HGV core to E1 could remain its epitope after purification, which showed the potential that G1 could be used as a coating antigen to develop an ELISA kit for HGV specific antibody diagnosis.

Expression, purification and bioactivity of human augmenter of liver regeneration

AIM： To construct the expression vectors for prokaryotic and eukaryotic human augmenter of liver regeneration （hALR） and to study their biological activity. METHODS： hALRcDNA clone was obtained from plasmid pGEM-T-hALR, and cDNA was subcloned into the prokatyotic expression vector pGEX-4T-2. The recombinant vector and pGEX-4T-2hALR were identified by enzyme digestion and DNA sequencing and transformed into E coli JM109. The positively selected clone was induced by the expression of GST-hALR fusion protein with IPTG, then the fusion protein was purified by glutathine s-transferase （GST） sepharose 4B affinity chromatography, cleaved by thrombin and the hALR monomer was obtained and detected by measuring H thymidine incorporation. RESULTS： The product of PCR from plasmid pGEM-T- hALR was examined by 1.5% sepharose electrophoresis. The specific strap was coincident with the theoretical one. The sequence was accurate and pGEX-4T-hALP digested by enzymes was coincident with the theoretical one. The sequence was accurate and the fragment was inserted in the positive direction. The recombinant vector was transformed into E coli JM109. SDS-PAGE proved that the induced expressive fusion protein showed a single band with a molecular weight of 41 kDa. The product was purified and cleaved. The molecular weights of GST and hALR were 26 kDa, 15 kDa respectively. The recombinant fusion protein accounted for 31% of the total soluble protein of bacterial lysate. HALR added to the culture medium of adult rat hepatocytes in primary culture and HepG2 cell line could significantly enhance the rate of DNA synthesis compared to the relevant control groups （P 〈 0.01）.CONCLUSION： Purified hALR has the ability to stimulate DNA synthesis of adult rat hepatocytes in primary culture and HepG2 cells in vitro, and can provide evidence for its clinical application.

Expression and purification of recombinant human hemangiopoietin in Escherichia coli

Objective:To express the soluble recombinant hemangiopoietin protein in E.coli BL21(DE3).Methods:Using human fetal live cDNA as a template,a partial cDNA fragment of HAPO coding N-terminal region was subcloned into plasmids pTrc99,pQE60 and pET32c to construct different recombinant prokaryotic expression systems.After selecting,the soluble rhHAPO fusion protein was expressed stably in E.coli BL21(DE3) by vector pET32c-HAPO and further isolated by nickelnitrilotriacetic acid(NTA) affinity chromatography.After cleavage with enterokinase,the rhHAPO protein was applied to Fast Flow SP sepharose column.Results:The rhHAPO protein had a purity of more than 95% and a good bioactivity based on the cell adhesion assay in ECV304 cells.Conclusion:We have established a protein engineering system to produce rhHAPO which may provide the possibility for clinical application.

Expression and Purification of Zinc Finger Domain and Central Domain of MDMD2

[ Objective] This study aimed to construct the His-tagged prokaryotic expression vectors harboring zinc finger domain （ZF） and central domain （ acidic domain ＆ zinc finger domain, CT） of MDM2, respectively, and preliminarily identified biologic activity of the purified fusion proteins. [ Method ] ZF and CT cod- ing regions were amplified from MDM2 cDNA library by PCR and separately inserted into prokaryotie expression vector pET28b to construct the recombinant plas- mids. After verification by enzyme digestion, the recombinant plasmids were separately transformed into E. coli DH5c~ competent cells. The expressed recombinant plasmids were purified using Ni-NTA magnetic beads and identified by SDS-PAGE and Western blotting. [ Result] The molecular weight of His-ZF and His-CT fu- sion proteins was 21 and 31 kD, respectively. E Conclusion] Recombinant fusion proteins containing ZF and CT of MDM2 were obtained successfully, which laid the foundation for subsequent protein crystallization and three-dimensional structure analysis.

Expression,purification and identification of LBD domain of human PPARδ in E.coli

Peroxisome proliferator-activated receptors （PPARs） are ligand-activated transcription factors known to play a pivotal role in regulations of metabolism. In order to yield soluble ligand binding domain of PPARδ （PPARδLBD） for screening ligands, the cDNA was amplified using total RNA from HepG2 cells by RT-PCR. Then the enzyme-digested product was inserted . downstream of the malE gene in the vectorpMAL-p2x, which encoded maltose-binding protein （MBP）, resulting in the expression of an MBP-PPARδLBD fusion protein. The recombinant plasmid was transformed into E. coli TBI that was cultured shakily at 30 ℃, 200 r/min and induced by 0.4 mmol/L IPTG for 6 h. The cells were harvested by centrifugation and broken by sonication. The expressed fusion protein was soluble and accounted for 0.31 of the total protein in the supernatant. Western blot analysis showed that the expressed MBP-PPARδLBD could bind to anti-MBP-antibody. The MBP-PPARδLBD fusion protein of 77 kDa and the PPARδLBD protein of 34 kDa were obtained by amylose-resin affinity chromatography without or with digestion of Factor Xa. They were both homogeneity, judged by SDS-PAGE. The recombinant MBP-PPARδLBD and PPARδLBD protein with high purity is obtained, which provides the necessary material for screening and researching PPARδ ligands.

Purification of the Drosophila melanogaster Proteins Inscuteable and Staufen Expressed in Escherichia coli

The proteins Inscuteable and Staufen are key components during asymmetric cell division of neuroblasts for the development of Drosophila melanogaster. Expression and purification of both proteins has been a difficult task for structure-function studies. Based on codon optimization for protein expression in Escherichia coli, we have been able to produce, in soluble form, the C-terminal domains of Inscuteable and Staufen as chimeras with N-terminal maltose binding protein tag that contains a rigid linker between them for feasible crystallization. In addition, using an optimized synthetic gene, corresponding to the amino acid region 250 - 623 of Inscuteable fused to glutathione-S-transferase, low-scale expression experiments showed production of soluble protein. Finally, eukaryotic expression of Inscuteable in the methylothropic yeast Pichia pastoris failed to produce the Drosophila protein at detectable amounts, reinforcing the fact that E. coli still was the microorganism of choice for high-yield protein expression.

Purification and identification of simian parvovirus protein Vp2 expressed in E.coli

To purify and identify the simian parvovirus （SPV） protein Vp2 expressed in E. coli, fusion protein of SPV Vp2 was expressed in E. coli DHSα competent cells transformed with vector pThioHis AVp2, and the new bacterial protein extraction reagent was used to extract the protein. Detergents with different characteristics were used to solubilize the fusion protein, and metal chelating resin （ProBond） with a continuous elusion polyacrylamide gel electrophoresis procedure was employed to purify the fusion protein. SDS-PAGE gel stained with coomassie blue and Western-blotting probed with anti-thio and anti-SPV Vp2 antibodies were used to identify the specificity of the expressed and purified fusion proteins. It was found that the SPV Vp2 protein expressed in E. coli was highly insoluble, and could not be solublized by the commonly used detergent. However, 6 M urea could solubilize the fusion proteins and was then employed for the further purification procedure, but metal chelating resin could not be used for this procedure, because of the loss of the tertiary structure of HP-thiaoredoxin and the metal-binding domain. The technique with continuous elusion polyacrylamide gel electrophoresis yielded a homogenous protein with a single band on the gel stained with coomassie blue and retained reactivity with anti-thio or anti-SPV Vp2 antibodies. It is evident that this technique with successful purification of SPV Vp2 protein has practical significance for the further investigation on the simian parvovirus infection.

CLONING SEGMENT SPIKE PROTEIN GENE OF SARS-COV AND ITS EXPRESSION IN ESCHERICHIA COLI

Objective Expressing and purifying the segment of SARS-CoV spike protein in E.Coli. Methods The target gene was obtained by RT-PCR. The PCR product was cloned into pEGM- T Easy Vector, sequencing and double restriction digestion ( BamHⅠ,PstⅠ) were performed. The target gene was subcloned into PQE30 expression vector. The gene was expressed in the E.coli strain M15 cells induced by IPTG. The protein was purified with a nickel HiTrap chelating metal affinity column. Results The recombinant expression plasmid was successfully constructed and the protein was well expressed in E. coli strain M15 cells. The ideal pure protein was obtained by purification. Western blotting analysis suggested the protein could act with the convalescent sera of lab confirmed SARS patients. Conclusion The segment of SARS-CoV spike protein was well expressed and purified, and can be applied in diagnosis and immunological research of SARS.

Purification and Analysis of Abscisic Acid-Specifically-Inducible Proteins from Rice Callus

Two ABA-specifically-inducible proteins from rice callus were isolated and purified by precipitation with 65-100% saturated （NH4）2SO4, followed by the DEAE-sepharose, TSK-gel, and two-dimension electrophoresis. Iso-electric points （pl） of the proteins with the same molecular mass （24.5 kD） were 6.1 and 6.9, respectively. The Western blot analysis indicated that the proteins expressed in different tissues were obviously different. The A1 （pl 6.1） protein was only detected in calli treated with ABA and seed embryos （SE）. However, the A2 （pl 6.9） protein was found not only in the calli treated with ABA and SE, but also in the white dry callus. Thus it suggested that the two proteins might play some important roles in the processes of seed embryo （or somatic embryo） formation.

Efficient and Soluble Expression of α Protein of Clostridium perfringens and Preparation of Genetic Engineering Subunit Vaccine

[Objective] The paper was to develop genetic engineering vaccine that can express α exotoxin antigen protein efficiently without destroying its immunogenicity for preventing and controlling the diseases caused by Clostridium perfringens. [Method] Efficiently expressed soluble recombinant α protein was obtained from Escherichia coli expression system by optimizing codon,removing signal peptide,selecting sequences with better hydrophilicity and antigenicity,and optimizing expression conditions. [Result] Mice obtained higher serum antibody level when immunized by α protein,and the immune protection rates against type A,type B,type C and type D C. perfringens were 100%,90%,85% and 90%,respectively. The antibody titer of mice within 7-14 d after the third immunization reached the peak. [Conclusion]The α protein has good immunogenicity,and can be further used to develop genetic engineering subunit vaccines for preventing C. perfringens.

Expression and Characterization of Human Heart Type Fatty Acid Binding Protein in Pichia Pastoris

H-FABP is regarded as a tissue-specific protein existing only in myocardial cells. It is released from the cardiac tissue and gets into the plasma when a heart attack occurs; the myocardial infarction is a good case in point. As a resuit, the detection of H-FABP will be an early and important biomarker for the disease concerned. The objective of the study is to prepare the recombinant H-FABP by aeukaryotic expression system, pichia, to produce the protein mimicking natural H-FABP, as an immunogen for the production of the specific antibody. A gene fragment encoding H-FABP was cloned in the expressing vector pPICZα, after sequencing. The recombinant plasmid was transformed into the competent cells of the X-33 strain by means of electroporation. The expression of the target peptide induced by methanol was screened by means of Western hlotting, with the available MAb（Clone 6B6）. Highly expressive engineer strains were obtained. The production of recombinant H-FABP under induction was about 0.7 g/L, with an Mr of 14.5 kDa and recognized by a commercially available MAb （Clone 6B6）. The recombinant vector was successfully constructed. Following this, H-FABP was expressed in X-33, and it would become the source of the preparation of specific antibodies, to develop diagnostic kits.