High-level soluble expression of phospholipase D from Streptomyces chromofuscus in Escherichia coli by combinatorial optimization

BACKGROUND: Phospholipase D (PLD) is used as the biocatalyst for phosphatidylserine (PS) production. In general, PLD was expressed in insoluble form in Escherichia coli. High-level soluble expression of PLD with high activity in E. coli is very important for industrial production of PLD. RESULTS: Streptomyces chromofuscus PLD coding gene was codon-optimized, cloned without signal peptide, and expressed in E. coli. The optimal recombinant E. coli pET-28a+PLD/BL21(DE3) was constructed with pET-28a without His-tag. The highest PLD activity reached 104.28 ± 2.67 U/mL in a 250-mL shake flask after systematical optimization. The highest PLD activity elevated to 122.94 ± 1.49 U/mL by feeding lactose and inducing at 20 C after scaling up to a 5.0-L fermenter. Substituting the mixed carbon source with 1.0 % (w/v) of cheap dextrin and adding a feeding medium could still attain a PLD activity of 105. 81 ± 2.72 U/mL in a 5.0-L fermenter. Fish peptone from the waste of fish processing and dextrin from the starch are both very cheap, which were found to benefit the soluble PLD expression. CONCLUSIONS: After combinatorial optimization, the high-level soluble expression of PLD was fulfilled in E. coli. The high PLD activity along with cheap medium obtained at the fermenter level can completely meet the requirements of industrial production of PLD.

Prokaryotic expression and one-step purification of soluble diphtheria toxin variant CRM197 / 基础医学与临床

Objective To construct a novel prokaryotic expression system, in which cross-reacting material 197 (CRM197) can be expressed in a soluble form in Escherichia coli(E. coli) cytoplasm and purified simply by one-step Ni-NTA affinity purification. Methods The CRM197 coding sequence was cloned into the prokaryotic expres-sion vector pET-32a(+) as an fusion protein with Trx tag,the HRV3C(human rhinovirus 3C) protease recognition sequence and 6 histidine sequence were added to the N-terminal of CRM197.HRV3C protease gene was cloned into another prokaryotic expression plasmid pGArasd. Both plasmids were co-transformed into E. coli Origami B (DE3) and induced mildly at 15℃. CRM197 recombinant protein was purified by Ni-NTA affinity matrix. Results The free soluble His-tagged CRM197 protein was released by cleavage of the accompanying expressed HRV3C protease after the CRM197 fusion protein was expressed. After one-step affinity purification recombinant CRM197 protein with a purity of almost 95% was obtained. Outcoming of the final preparation incubated with DNA indicated the pu-rified CRM197 recombinant protein has deoxyribonuclease activity. Conclusions By constructing a novel double-plasmid auto-cleavage prokaryotic expression system in this study, the production process of obtaining soluble CRM197 recombinant protein in E. coli has been simplified,with expression and purification efficiency improved and the production cost reduced.

Expression, purification and characterization of diphtheria toxin mutant CRM197 in Eschrichia coli / 生物工程学报

CRM197 (cross-reacting material 197), a non-toxic mutant of diphtheria toxin, has wide application potential in biopharmaceuticals. However, it is difficult to express CRM197 in bacteria other than Corynebacterium diphtheriae. Here we proposed a new alternative method to produce soluble CRM197 without label in Escherichia coli. In particular, a synthetic gene coding for CRM197, optimized for E. coli codon usage, was cloned in the pET32a (+) vector. Accordingly, the over-expression of the protein was simply induced with IPTG in E. coli BL21 (DE3). The target protein was soluble and accounted for about 40% of the total protein in the supernatant. Following an ultrasonic cytolysis step, the recombinant protein was purified by anion exchange, affinity and desalting chromatography and the purity of the final preparation reached 95%. Cytotoxicity tests showed that the IC₅₀ value of CRM197 was 2.1×10⁷ times the IC₅₀ value of diphtheria toxin, and 9.6 times the IC50 value of diphtheria toxoid, telling that the target protein is safe and non-toxic. Subsequently, we found that both the high dose (20 μg) and the low dose (2 μg) of CRM197 were equally efficient in inducing an immune response against diphtheria toxiod in mice, and the antibodies titer of mice after three immunizations with low dose could reach 1:409 600. In conclusion, our findings provide a highly efficient strategy for the rapid production and purification of unlabeled and soluble recombinant CRM197 in E. coli, with good immunogenicity and safety.

Design and immunogenicity evaluation for the bacteria-like particle vaccine against swine type O foot-and-mouth disease virus / 生物工程学报

Based on gram positive enhancer matrix displaying technology, we designed and evaluated a bacteria-like particle vaccine against swine type O Foot-and-mouth disease virus. Three optimized genes of type O Foot-and-mouth disease virus strain Mya98 were cloned into recombinant prokaryotic expression vector pQZ-PA and renamed as pQZ-BT1B-PA, pQZ-BT2B-PA and pQZ-B (T1BT2) 4B-PA, fused with an anchor protein (PA) binding to Gram-positive enhancer matrix (GEM) particles specifically. The protein expression was identified with SDS-PAGE and Western blotting, and then purified with GEM particles. Five-week old female mice were randomly divided into six groups and all the immunization was developed according to subcutaneous injection. Mice in the first three groups were injected with 50 μg/dose GEM-BT1B, GEM-BT2B and GEM-B (T1BT2) 4B, respectively. Mice in the fourth group were immunized with commercial peptide vaccine as positive control. The fifth group vaccinated with host E. coli transformed with pQZ-PA fulfilled as negative control. Mice in the last group injected with sterile PBS served as blank control. The humoral immunity of recombinant protein vaccine was evaluated with peptide-specific antibody and LPB antibody. The cellular immunity was evaluated with lymphocyte proliferation test and cytokine expression detection. SDS-PAGE and Western blotting showed that the most part of soluble target fusion protein have been purified and displayed on GEM particles. Vaccine GEM-B (T1BT2) 4B stimulated mice produce not only higher level of specific antibody against peptide and Foot-and-mouth disease virus specific liquid phase blocking antibody, but also more vigorous spleen lymph proliferation and higher levels of Th1 type cytokines. To summarize, vaccine of GEM-B (T1BT2) 4B possessed good immunogenicity and opened a new way for further Foot-and-mouth disease virus subunit vaccine design.

Clone and soluble fusion expression ofα-HL of Staphylococcus aureus / 中国免疫学杂志

Objective:Expression and purification of the α-HL of Staphylococcus aureus as antigen for making full human anti-α-HL antibody later ,providing of new treatment for Staphylococcus aureus infection.Methods:The total RNA of Staphylococcus aureus was extracted and the cDNA of α-HL was amplified by RT-PCR.The DNA of α-HL and pCold-TF plasmid was digested and ligated by T4 ligase and then transformed into E.coli TOPO 10.The recombinant plasmid α-HL/pCold-TF which verified by sequencing was trans-formed into E.coli BL21 for expression.The expression products was identified by SDS-PAGE and Western blot.Results: The size of amplified cDNA of α-HL was about 900 bp and the expressed soluble fusion protein of α-HL was about 90 kD(including the molecular chaperone in the vector ) after inducing expression for 24 h at 15℃.The Western blot results showed that the expressed protein was the fusion protein of α-HL.The purified α-HL was injected into BABL/c mice for making antiserum.The results showed that the antiserum had good binding activity with Staphylococcus aureus and the titer was greater than 10 000 times.Conclusion: The α-HL of Staphylococcus aureus was successfully cloned and the soluble fusion protein of α-HL was successfully expressed.

A Novel Polyclonal Antiserum against Toxoplasma gondii Sodium Hydrogen Exchanger 1

The sodium hydrogen exchanger 1 (NHE1), which functions in maintaining the ratio of Na+ and H+ ions, is widely distributed in cell plasma membranes. It plays a prominent role in pH balancing, cell proliferation, differentiation, adhesion, and migration. However, its exact subcellular location and biological functions in Toxoplasma gondii are largely unclear. In this study, we cloned the C-terminal sequence of T. gondii NHE1 (TgNHE1) incorporating the C-terminal peptide of NHE1 (C-NHE1) into the pGEX4T-1 expression plasmid. The peptide sequence was predicted to have good antigenicity based on the information obtained from an immune epitope database. After induction of heterologous gene expression with isopropyl-b-D-thiogalactoside, the recombinant C-NHE1 protein successfully expressed in a soluble form was purified by glutathione sepharose beads as an immunogen for production of a rabbit polyclonal antiserum. The specificity of this antiserum was confirmed by western blotting and immunofluorescence. The antiserum could reduce T. gondii invasion into host cells, indicated by the decreased TgNHE1 expression in T. gondii parasites that were pre-incubated with antiserum in the process of cell entry. Furthermore, the antiserum reduced the virulence of T. gondii parasites to host cells in vitro, possibly by blocking the release of Ca2+. In this regard, this antiserum has potential to be a valuable tool for further studies of TgNHE1.

Expression and purification of soluble single-chain Fv against human fibroblast growth factor receptor 3 fused with Sumo tag in Escherichia coli

Background Overexpression or mutated activation of Fibroblast growth factor receptor 3 (FGFR3) is involved in the pathogenesis of many tumors. More and more studies focus on the potential usage of therapeutic antibodies against FGFR3. Results In this study, a novel single-chain Fv (ScFv) against FGFR3 was prepared and characterized. To achieve the soluble expression, ScFv was fused with Sumo (Small ubiquitin-related modifier) by polymerase chain reaction (PCR), and cloned into pET-20b. The recombinant bacteria were induced by 0.5 mM Isopropyl-ß-d-thiogalactopyranoside (IPTG) for 16 h at 20°C, and the supernatant liquid of Sumo-ScFv was harvested and purified by Ni-NTA chromatography. After being cleaved by the Sumo protease, the recombinant ScFv was released from the fusion protein, and further purified by Ni-NTA chromatography. The purity of ScFv was shown to be higher than 95% and their yield reached 4 mg per liter of bacterial culture. In vitro data showed that ScFv can significantly attenuate FGF9-induced phosphorylation of FGFR3. Conclusion We provide a novel method to produce soluble expression and bioactive functions of ScFv in Escherichia coli.

Soluble expression, purification and characterization of recombinant Tp0136 selective fragment from Treponema pallidum / 中华微生物学和免疫学杂志

Objective To express and purify recombinant Tp0136 epitope fragment, and study the immunity activity. Methods The Tp0136 selective fragment(Tp0136B) gene was devised by the surface property analysis, solvent-accessible suface calculateions, secondary structure function region analysis, and was inserted between the sites of Nde Ⅰ and Not Ⅰ in pET22b ( + ) . The recombinant plasmid was expressed in E. coli BI21. After nickel ion metal affinity chromatography, the antigenic and immune reactivity of rTp0136B was confirmed. Then indirect ELISA with the rTp0136B as coating antigen was performed to detect the anti-Tp0136 antibody in sera from 100 normal human controls and 131 primary syphilis patients. Results The rTp0136B was soluble expressed with a molecular weight of about 28 000 and was obtained with a purity of ＞98% by chromatography. Western blot proved that the rTp0136B could specifically react with anti-Tp0136 polyclonal antibody. Specific humoral response was elicited by the recombinant protein in Japan negative. The positive detection rate in sera from primary syphilis patients was 85.5%. Conclusion This result suggested that the recombinant Tp0136 epitope fragments have a satisfactory immunocompetence,which may have applications in the serodiagnosis of primary syphilis.

The soluble expression and identification of single-chain fragment V antibodies against SSA antigen epitopes from the pHEN2 phagemid library / 中华内科杂志

Objective To obtain the soluble single-chain fragment V (ScFv)monoclonal antibodies (McAbs) against the SSA antigen epitopes.Methods Three octapeptides (60 000 SSA antigen residues 482-493 termed as P1 epitope, residues 310-323 termed as P2 epitope and residues 230-241 termed as P3 epitope) were synthesized on the lysine frame.The McAbs were panned by coating the corresponding as targets.The specificity, affinity and gene squences of the positive clones were assessed.Soluble single-chain fragment V antibodies special for SSA antigen epitopes were expressed and then identificated.Results After 5 rounds of panning, reactive scFv clones contained full-length scFv antibodies coding regions were obtained,with sufficient affinity and specificity for respective antigen peptides.The absorbance values at 410 nm of the fusion protein of anti-P1-P3 activity with the corresponding peptides were 1.43 ± 0.23, 0.82 ±0.31 and 0.80 ± 0.25, and there was also statistically significant difference in the cross reactions ( P ＜ 0.01 ).Three clones were successfully expressed and then purified by His-bind resin.The activity in vivo of soluble ScFv antibodies was identified to be positive by the indirect immune-fluorescence assay on Hep-2 cells.Conclusion Souble ScFv McAbs against corresponding SSA antigen peptides with high affinity,specificity and activity in vivo were obtained, which are to be competent enough for epitopes expression on the target organs.

Soluble expression, purification and bioactivity of hemangiopoietin protein / 细胞与分子免疫学杂志

AIM: To prepare a soluble hemangiopoietin(HAPO) protein and to construct pET22b(+) expression vector, to obtain pure recombinant HAPO protein and to measure its bioactivity. METHODS: HAPO cDNA was amplified using RT-PCR method from a commercial human fetal liver cDNA library. The resulting product was cloned into pET22b(+) vector and transformed into E.coli BL21(DE3). The recombinant protein was isolated and purified by Ni~(2+)-NTA chelating resin and the chromatographies of SP Sepharose FF. The adhesion of human umbilical vein endothelial cells (HUVEC) were measured by adhesion assay. RESULTS: HAPO gene with a reading frame of 897 bp was successfully cloned from human fetal liver cDNA library, the expressed pET22b(+)-HAPO fused protein existed in a soluble form, with the yield above 10% total bacterial protein and its purity achieved above 80%. The activity assay showed that the treatment of HAPO enhanced total adherence of HUVEC in a concentration-dependent manner. CONCLUSION: HAPO protein can be expressed in a soluble form. HAPO may facilitate the homing of hematopoietic stem/progenitor cells in vitro.

Soluble expression of a CXCL10-loop3-EGF fusion protein and its anti-tumor activity / 中国病理生理杂志

AIM: To evaluate the implication of CXCL10-loop3-EGF fusion protein for the activities of targeting tumor and anti-angiopoiesis. METHODS: RT-PCR was preformed to amplify CXCL10 coding sequence from PBMC activated by IFN-γ. CXCL10-loop3-EGF fusion gene, which was conducted by Over-Lap Extention PCR, was hinged up with plasmid pTG19-T, transfected to E. coli DH5α and processed positive colony selection. After ligated with plasmid pET32a(+), recombinant CXCL10-loop3-EGF fusion gene was then transfected to E. coli Origami B (DE3) and induced to express its coding fusion protein his-CXCL10-loop3-EGF. The recombinant fusion protein CXCL10-loop3 -EGF was purified by His-bind affinity chromatograph, enterokinase cleavage, ultrafiltration and dislysis. The transwell chemotatic test and HUVEC angiopoiesis inhibition test were performed to determine the anti-tumor responses and anti-angiopoiesis activity of CXCL10-loop3-EGF fusion protein. RESULTS: CXCL10-loop3-EGF fusion protein was successfully constructed and confirmed by SDS-PAGE analysis and Western blotting. Significant PBMC chematatic activity and HUVEC anti-angiopoiesis activity were observed. CONCLUSION: CXCL10-loop3-EGF fusion protein, which has perfect anti-tumor activity, is successfully constructed.

Expression and Activity of Recombinant Human Glutamate Decarboxylase 65 / 中国生物工程杂志

Human glutamate decarboxylase 65(hGAD65) is an enzyme that catalyzes the transformation of L-glutamic acid into ?-aminobutyric acid.It has been found that Type 1 diabetes mellitus(T1DM)is an autoimmune disease,in which pancreatic islet ?-cells are destroyed due to immune response mediated by autoantigen.hGAD65 is considered as a key autoantigen of the autoimmune response,so anti-hGAD65 antibody(hGAD65-Ab) is the most effective and specific immune marker for T1DM diagnosis,and hGAD65 can be used to detect hGAD65-Ab in serum of T1DM patients.The hGAD65 gene was cloned into pET32a(+),then the recombinant plasmid with hGAD65 was transformed into E.coli BL21(DE3) and expressed by IPTG induction.The fusion protein containing thioredox,hexahistidine and hGAD65(Trx-hGAD65) was mostly insoluble,but the band of soluble Trx-hGAD65 could also be detected by SDS-PAGE,and it was a great improvement compared with the results reported.Trx-hGAD65 was isolated from lysate and purified by immobilized metal ion affinity chromatography(IMAC).After enterokinase digestion and IMAC purification,hGAD65 with high purity was obtained.Detection of thin-layer chromatography(TLC) showed that both Trx-hGAD65 and hGAD65 had enzymatic activity,whereas Trx-hGAD65 had better stability.Furthermore,it was confirmed that Trx-hGAD65 was able to conjugate with hGAD65-Ab in the serum of T1DM patients by ELISA assay.In conclusion,Trx-hGAD65 instead of hGAD65 can be used for T1DM diagnosis,and its application in prophylaxis and therapy of T1DM is expectable.

Soluble Expression and Purification of Snake Venoms Fihrino(geno)lytic Emzyme Alfimeprase in E.coli / 中国生物工程杂志

Fibrolase is a non-hemorrhagic zinc metalloproteinase isolated from southern copperhead snake venom (Agkistrodon contortrix contortrix) and is capable of degrading fibrin clots resulting from purified fibrinogen or from blood plasma. Alfimeprase, a truncated form of fibrolase, as a clinical agent was successfully completed PhaseII clinical trials.The cDNA of alfimeprase was amplified by recursive PCR, digested with BamHI and HindII, and cloned into pET43.1a, pMALp2X and pMALc2X vectors to generate fusions with NusA, MBP and sMBP(with signal peptide), respectively. Nus/alfimeprase was expressed in soluble form by co-expressing with chaperone FkpA and inducing with1mmol/L IPTG. The fusion protein accounted for about 25 % of total protein following cell lysis. Alfimeprase was successfully purifiesd by Ni-NTA affinity chromatography and cleaved by enterokinase. The results demonstrate the fibrinolytic activity of recombinant alfimeprase using fibrin plate assays and fibrinogen hydrolysis.

Development and Identification of Monoclonal Antibodies against the Recombinant P38 Antigen of Schistosoma japonicum / 中国寄生虫学与寄生虫病杂志

Objective To express P38 of Schistosoma japonicum in Escherichia coli BL21 and develop the monoclonal antibodies (McAb) against rSjP38. Methods The recombinant plasmid pET32(a)-P38 was transformed into E.coli BL21(DE3). 1 mmol/L IPTG (isopropyl-beta D-thiogalactopyranoside) was used to induce the expression of the recombinant rSjP38. The rSjP38 was soluble in supernatant after sonication and further purified by His-Ni chromatography. BALB/c mice were immunized with the purified rSjP38 and hybridomas were generated with traditional technique. McAbs were screened by ELISA with limited dilution. The subtype and specificity of McAb were identified by kit and Western blot respectively. Results Eight hybridoma cell lines secreting monoclonal antibodies to rSjP38 were obtained. The subtype of all the 8 McAbs are IgG1. Western blotting showed that the 8 McAbs reacted strongly and specifically with native antigen (P38) of Schistosoma japonicum. Conclusions Eight hybridoma cell lines secreting highly specific McAbs against P38 have been established.