Recombinant expression of black sesame polyphenol oxidase and its enzymatic properties / 生物工程学报

To investigate the enzyme properties of the black sesame polyphenol oxidase (BsPPO), a synthesized Bsppo gene was cloned into the vector pMAL-c5x and expressed in E. coli. Subsequently, the MBP fusion label in the recombinant protein was removed by protease digestion after affinity purification. The synthesized Bsppo gene contained 1 752 bp which encodes 585 amino acids with a deduced molecular weight of 65.3 kDa. Transformation of the recombinant vector into E. coli BL21(DE3) resulted in soluble expression of the fusion protein MBP-BsPPO. The enzymatic properties of the recombinant BsPPO was investigated after MBP fusion tag excision followed by affinity purification. The results demonstrated that the optimal temperature and pH for BsPPO was 25°C and 4.0, respectively. BsPPO exhibited a good stability under low temperature and acidic environment. Low-intensity short-term light exposure increased the activity of BsPPO. Cu²⁺ could improve the activity of BsPPO while Zn²⁺ and Ca²⁺ showed the opposite effect. BsPPO could catalyze the oxidation of monophenols, diphenols, and triphenols, and exhibited good catalytic activity on l-tyrosine and vanillic acid. Moreover, BsPPO exhibited high catalytic activity on black sesame metabolites, including 2-methoxy cinnamic acid, indole-3-carboxylic acid and phloretin. These results may serve as a basis for further characterization of BsPPO.

Cloning, expression and purification of novel gene Rv2742 in Mycobacterium tuberculosis H37Rv / 生物工程学报

Rv2742 is a novel gene identified from Mycobacterium tuberculosis H37Rv by the proteogenomics strategy. The aim of this study was to establish a system of soluble expression and purification of the missing protein Rv2742 in M. tuberculosis H37Rv, to provide reference for further research on the biological function of Rv2742. The soluble protein was not successfully induced by prokaryotic expression vectors pGEX-4T-2-Rv2742, pET-32a-Rv2742, pET-28a-Rv2742 and pMAL-c2X-Rv2742. After the codon of novel gene Rv2742 was optimized according to E. coli codon usage frequency, only the recombinant strain containing plasmid pMAL-c2X-Rv2742 could produce soluble products of Rv2742 encoding gene. In addition, the expression effects of the desired fusion protein were also analyzed under different conditions including hosts, culture temperatures and IPTG concentrations. The optimum expression conditions were as follows: Rosetta (DE3) host, 16 °C culture temperature and 0.5 mmol/L IPTG. After being purified by affinity chromatography with amylose resin, the fusion protein sequence was confirmed by LC-MS/MS. These results indicated that the novel gene Rv2742 product could be successfully induced and expressed in a soluble form by the expression system pMAL-c2X with MBP tag. Our findings provide reference for studies on potential interaction and immunogenicity.

Expression, purification and activity verification of human norovirus NS6 protein / 中华实验和临床病毒学杂志

Objective@#To express the NS6 nonstructural protein of human norovirus (NoV) in Escherichia coli, and to detect its enzymatic activity after purification.@*Methods@#Human NoV NS6 gene was cloned into the prokaryotic expression vector pDE1 and then was transformed into E. coli BL21 for expression. NS6 protein was purified by Ni-NTA affinity chromatography and Superdex 200 pg column. The activity of NS6 protein was determined by digestion of fusion protein 15VP1-6P at 37 ℃.@*Results@#Human NoV NS6 protein was stably and highly expressed in E. coli. After purification, the expressed product reached a purity of more than 95%, and the relative molecular weight of NS6 protein was about 23×103 Da. NS6 protein could cleave the fusion protein containing rhinovirus 3C cleavage site.@*Conclusions@#The nonstructural protein NS6 of human NoV was successfully expressed in Escherichia coli, which laid a foundation for further study on the pathogenesis of human NoV.

Application of inteins in building protein affinity purification system / 生物工程学报

Intein is a part of polypeptide in the premature protein with the capability of self-splicing, which is widely applied in protein purification, protein conjuction, cyclopeptide preparation, protein labeling and biosensor. In this review, we summarized the development of intein used in protein purification, discussed intein-mediated chromatographic and non-chromatographic purification systems, and summarized the researches in manipulating intein cleavage reaction. This work is to provide clues for improvement of intein-mediated protein purification.

Prokaryotic expression and purification of Chlamydomonas reinhardtii intraflagellar transport protein 46(IFT46) and preparation of polyclonal antibody / 生物工程学报

IFT46 is one of the important components of intraflagellar transport complex B in Chlamydomonas reinhardtii, and plays important roles in the assembly, movement and perception of ciliary. To study its functional mechanism, a GST-tagged and an MBP-tagged prokaryotic expression plasmid, pGEX-2T-ift46 and pMAL-C2X-ift46 were constructed, respectively, by inserting ift46 into the pGEX-2T and pMAL-C2X vector, and then transformed into Escherichia coli BL21 (DE3) for protein expression. SDS-PAGE (15%) analysis results showed that the molecular weights of the fusion protein GST-IFT46 and MBP-IFT46 were 70 kDa and 86 kDa, respectively. We used the fusion protein GST-IFT46 purified by affinity adsorption purification (more than 95% purity) for immunity to New Zealand white rabbits. The 5th immune serum was collected and the antibody titer was determined to be 256 000 by ELISA. The antiserum was purified by Protein A affinity adsorption purification and immobilized MBP-IFT46 purification, and the specificity of polyclonal antibodies was evaluated by Western blotting and immunofluorescence. Results showed that the polyclonal antibody prepared could specifically and precisely bind IFT46 in C. reinhardtii, and IFT46 was mainly concentrated at basal body regions and few localized along the entire length of the flagellum as punctuated dots, which will make a foundation to further study the mechanism of IFT46 in cilia related diseases such as obesity, diabetes and polycystic kidney disease.

Efficient Expression and Purification of Recombinant Human Enteropeptidase Light Chain in Esherichia coli

Human enterokinase (synonym: enteropeptidase, EC 3.4.21.9) light chain (hEKL) gene was designed and artificially synthesized with built-in codon blas towards Escherichia coli codon preference. The synthetic hEKL gene was cloned into prokaryotic expression vector pMAL-s and transferred into the expression strain E. coli BL21 (DE3). Recombinant hEKL protein with a maltose binding protein (MBP) tag was expressed at high levels in soluble form, which yielded about 42% of the total cellular protein. The target protein was then purified to the homogeneity (> 95%) by affinity chromatography. The peptide substrate GST-Melittin with enterokinase recognition site was completely cleaved by the purified MBP-hEKL at the molar ratio of 1:5000 (enzyme:substrate). Tricine SDS-PAGE analysis showed that the activity of MBP-hEKL was approximately seven times that of bovine enterokinase catalytic subunit (EKMaxTM, Invitrogen). From 1 L flask culture, 206 mg pure active MBP-hEKL was with specific activity of 1.4×104 U/mg.

Expression, purification and biological activities assay of human C1q and tumor necrosis factor related protein-6 / 中国药理学通报

Aim To prepare soluble human C1 q and tumor necrosis factor related protein-6 in Escherichia coli and analyze the bioactivity. Methods Recombi-nant plasmid was transformed into E. coli expression strain, and the recombinant protein Trx-hCTRP6 was expressed induced by IPTG and then purified. Results Trx-hCTRP6 was expressed efficiently and purified using Ni-NTA affinity chromatography and Superdex G-75 column. The purified Trx-hCTRP6 was shown to be active under in vivo and in vitro assay conditions. Con-clusion Active Trx-hCTRP6 is efficiently prepared from E. coli protein expression system.

Construction of three new Gateway® expression plasmids for Trypanosoma cruzi

We present here three expression plasmids for Trypanosoma cruzi adapted to the Gateway® recombination cloning system. Two of these plasmids were designed to express trypanosomal proteins fused to a double tag for tandem affinity purification (TAPtag). The TAPtag and Gateway® cassette were introduced into an episomal (pTEX) and an integrative (pTREX) plasmid. Both plasmids were assayed by introducing green fluorescent protein (GFP) by recombination and the integrity of the double-tagged protein was determined by western blotting and immunofluorescence microscopy. The third Gateway adapted vector assayed was the inducible pTcINDEX. When tested with GFP, pTcINDEX-GW showed a good response to tetracycline, being less leaky than its precursor (pTcINDEX).

High-level soluble expression of the functional peptide derived from the C-terminal domain of the sea cucumber lysozyme and analysis of its antimicrobial activity

Background The sea cucumber lysozyme belongs to the family of invertebrate lysozymes and is thought to be a key defense factor in protecting aquaculture animals against bacterial infection. Recently, evidence was found that the sea cucumber lysozyme exerts broad spectrum antimicrobial action in vitro against Gram-negative and Gram-positive bacteria, and it also has more potent antimicrobial activity independent of its enzymatic activity. To explore the antimicrobial role of this non-enzymatic lysozyme and model its structure to novel antimicrobial peptides, the peptide from the C-terminal amino acid residues 70-146 of the sea cucumber lysozyme in Stichopus japonicus (SjLys-C) was heterologously expressed in Escherichia coli Rosetta(DE3)pLysS. Results The fusion protein system led to over-expression of the soluble and highly stable product, an approximate 26 kDa recombinant SjLys-C protein (rSjLys-C). The present study showed that rSjLys-C displayed strong antimicrobial activity against the tested Gram-positive and Gram-negative bacteria. In particular, the heat-treated rSjLys-C exhibited more inhibitive activity than the native rSjLys-C. The structural analysis of SjLys-C showed that it is a typical hydrophilic peptide and contains a helix-loop-helix motif. The modeling of SjLys-C molecular structures at different temperatures revealed that the tertiary structure of SjLys-C at 100°C underwent a conformational change which is favorable for enhancing antimicrobial activity. Conclusion These results indicate that the expressed rSjLys-C is a highly soluble product and has a strong antimicrobial activity. Therefore, gaining a large quantity of biologically active rSjLys-C will be used for further biochemical and structural studies and provide a potential use in aquaculture and medicine.

Prokaryotic Expression and Antifungal Activity of HumanαDefensin-5 Protein / 天津医药

Objective To construct the prokaryotic expression vector for HD-5 and purify the recombinant HD-5 protein then analyze its antifungal activity. Methods The HD-5 gene was cloned by PCR, then was inserted into prokary-otic expression plasmid pQE-30Xa to construct pQE-30Xa/HD-5. After sequencing, pQE-30Xa/HD-5 was transformed in-to E.coli M15 cells. Its expression was induced by IPTG and confirmed by SDS-PAGE. The recombinant protein was purified through Ni-NTA affinity purification system. The antifungal activity was tested by disk diffusion method. Results HD-5 gene and pQE-30Xa/HD-5 vector were obtained successfully. E.coli M15 strains was used to express HD-5 fusion protein. After purification, the fusion protein was confirmed by Western blot. The disk diffusion test confirmed that the fusion pro-tein can inhibit Candida albicans. Conclusion Expression vector pQE-30Xa/HD-5 was successfully constructed. The HD-5 fusion protein was expressed in E.coli successfully, which showed a certain degree of antifungal activity.

Preparation of high specific antibody against human C1q/TNF-related protein-1 / 国际药学研究杂志

Objective: To prepare specific antibody against human C1q/TNF-related protein-1 (hCTRP1). Methods: A C-terminal antigenic peptide of hCTRP1 was synthesized and injected into the Newzealand rabbits. The antibody was purified by affinity chromatography column. Results: High titer antisera against the hCTRP1 was prepared and the antiserum's titration was over 1: 64 000 by indirect ELISA. The specificity of the purified antibody by affinity chromatography was identified by Western blot and ELISA. Conclusion: The high titer antiserum is prepared by injection for rabbits and the specificity of the antibody purified from the antiserum is determined.

Expression,purification and biological activity assays of global human C1 q and tumor necrosis factor related protein-2 / 中国药理学通报

Aim To prepare soluble global human C1 q and tumor necrosis factor related protein-2 in Escherichia coli. Methods Recombinant expression plasmid was transformed into strain BL21-codonplus (DE3),and the recombinant protein of Trx-gH2 was expressed by IPTG induction and then purified by Ni-NTA affinity and gel filtration chromatography.Results The purified recombinant Trx-gH2 was shown to be active under in vi-vo and in vitro assay conditions.Conclusion Active recombi-nant global hCTRP2 is efficiently prepared from Escherichia coli protein expression system.

Cloning and expression of Dengue virus nonstructural protein 4A gene and affinity purification of its interacting proteins / 中华微生物学和免疫学杂志

Objective To clone and express Dengue virus nonstructural protein 4A (NS4A) gene and express in eukaryotic cells.Then,to isolate and purify and isolate cellular proteins interacted with NS4A.Methods With specific primers,NS4A gene fragment tagged with FLAG and HA (FLAG-NS4A-HA) was amplified by PCR and cloned into an expression vector,pSG5 vector.Recombinant plasmid was transfected into A549 cells by LipofectAMINETM2000.Transient expression of FLAG-NS4A-HA was detected by Western blot.The NS4A interacting proteins were isolated and purified by tandem affinity purification (TAP) system using HA and FLAG antibodies,and then assayed by silver stained SDS-PAGE.Results Dengue virus NS4A gene tagged with FLAG and HA was successfully constructed into pSG5 vector and expressed in A.549 cells.Silver stained SDS-PAGE showed that the expressed NS4A and two potential interacting proteins that interact with NS4A were isolated after TAP purification and SDS-PAGE.Conclusion Cellular proteins that potentially interacted with Dengue virus NS4A were successfully purified and isolated,which provided a basis for further research.

Prokaryotic expression of a novel mouse pro-apoptosis protein PNAS-4 and application of its polyclonal antibodies

Mouse PNAS-4 (mPNAS-4) has 96 percent identity with human PNAS-4 (hPNAS-4) in primary sequence and has been reported to be involved in the apoptotic response to DNA damage. However, there have been no studies reported of the biological functions of mPNAS-4. In studies conducted by our group (unpublished data), it was interesting to note that overexpression of mPNAS-4 promoted apoptotic death in Lewis lung carcinoma cells (LL2) and colon carcinoma cells (CT26) of mice both in vitro and in vivo. In our studies, mPNAS-4 was cloned into the pGEX-6P-1 vector with GST tag at N-terminal in Escherichia coli strain BL21(DE3). The soluble and insoluble expression of recombinant protein mPNAS-4 (rmPNAS-4) was temperature-dependent. The majority of rmPNAS-4 was insoluble at 37°C, while it was almost exclusively expressed in soluble form at 20°C. The soluble rmPNAS-4 was purified by one-step affinity purification, using a glutathione Sepharose 4B column. The rmPNAS-4 protein was further identified by electrospray ionization-mass spectrometry analysis. The search parameters of the parent and fragment mass error tolerance were set at 0.1 and 0.05 kDa, respectively, and the sequence coverage of search result was 28 percent. The purified rmPNAS-4 was further used as immunogen to raise polyclonal antibodies in New Zealand white rabbit, which were suitable to detect both the recombinant and the endogenous mPNAS-4 in mouse brain tissue and LL2 cells after immunoblotting and/or immunostaining. The purified rmPNAS-4 and our prepared anti-mPNAS-4 polyclonal antibodies may provide useful tools for future biological function studies for mPNAS.

Tandem affinity purification technique: an extraordinary valuable tool for purifying protein complexes / 基础医学与临床

It's a multi-protein complex and not single protein that accomplish most of cellular activity.Therefore,to identify and analyze the composition of protein complex is necessary for studying the function of proteins.Tandem affinity purification technique(TAP) enables the effective purification of complex under physiological conditions without knowledge of the complex composition and function.Now,it has been adapted to analyze the composition of the protein complexes in yeast.Combined with mass spectrometry,TAP can identify the interacting proteins of target protein and offer great help for opening protein interacting network and function out.

The Research on Expression and Purification of a Chimeric Anti-p185 Antibody / 中国生物工程杂志

The Her-2 proto-oncogene encodes a 185kDa transmenbrane glycoprotein p185 which has intrinsic tyrosine kinase activity. It is overexpressed in several malignant human tumors like breast cancer. A chimeric antibody by assembling a single-chain Fv antibody and a human IgG1 Fc fragment was constructed. This chimeric antibody reacts with tumor surface antigen p185c-erbB-2 specifically. In order to put the antibody into clinical application, two steps purification method was used to attain the antibody’s purity more than 95%. Both the lyophilized pharmaceutical formulations of the antibody were found. The formulations can keep the stability and activity of the antibody for at least one year. These results were the foundation of the chimeric antibody for cancer therapy.

Preparation,Characterization and application of monoclonal antibodies to recombinant human interferon—?2a / 中国免疫学杂志

In this report,five mouse hybridoma cell lines secreting monoclonal antibodies to recombi-nant human interferon—?2a(rHu IFN—?2a)were raised.All the monoclonal antibodies with IgGl subclass react with rHu IFN—?2a detected by indirect ELISA with the titers ranging from 1:320,000 to 1:10,240,000 but have no cross reactivity with rHu IFN?l,? and proteins from recombinant E.coli.Two of monoclonal antibodies,designated 3F1 and 5G10,have the ability to neutralize antiviral activity of rHu IFN—?2a.By a competitive ELISA the five monoclonal anti-bodies can be divided into three categories based on their epitope specificities.A sandwich ELISA established by employing 3F1 and 5G10 monoclonal antibodies could detect rHuIFN-?2a or rHuIFN-?2b as few as 60pg/ml?Moreover,3F1 monoclonal antibody displayed a satisfactoryproperty in affinity chromatography for rHuIFN?2a,which is able to match a monoclonal anti-body NK2 from CellTech Corporation.

COMPARATIVE STUDIES ON PURIFICATION OF ENGINEERED ANTI-HBSFAB WITH 3 DIFFERENT METHODS / 解放军医学杂志

The purpose of this study was to compare the efficiency of 3 different methods in purifying engineered anti-HBsFab. Anti-HBsFab Supernatants containing anti-HBsFab were prepared by ultrasound lysis of host cells of anti-HBsFab positive clone. Anti-Fab-sepharose gel, streptococcal protein G-sepharose gel (Prot G gel) and Ni-NTA-agarose gel were used to purify Fabs according to the reagents protocols. Then the concentrations of purified proteins were determined. SDS-PAGE was used for the measurement of purified Fabs'purity. HBsAg based ELISA was chosen to determine the Fabs' bio-activity. The results indicated that Fab recovery of different gels in equal volume were different. The recovery of Ni-NTA GEL was greater than that of Prot G gel, and the recovery of Prot G gel was greater than that of anti-Fab gel. Purity of the Fab isolated by 3 different gels was confirmed by SDS-PAGE. The binding capacity of anti-HBs Fab to HBsAg of these three gels had no signifticant difference. Our data suggested that each method had its advantage and usage limitation, Ni-NTA method demonstrated much better performance in economy, management, and efficiency over the other two methods.