人肽抗生素hPABβ重组质粒的构建及其在大肠杆菌中的表达

Construction of recombinant plasmid harboring human peptide antibiotic gene hPAB-β and its expression in E. coli

目的 构建人肽抗生素hPAB β重组质粒 ,并在大肠杆菌中进行表达 ,为大量制备hPAB β奠定基础。方法 通过PCR将hPAB β融合蛋白的CNBr裂解位点改为羟胺裂解 ,将修改的目标片段克隆到pFAST HTa质粒中 ,挑取阳性重组子 ,酶切出目标片段再亚克隆到pQE32 CP中 ,含阳性重组子的工程菌用IPTG诱导表达 ,SDS PAGE电泳分析 ,进一步以亲和层析纯化融合蛋白 ,用羟胺裂解分析。结果 构建的pFAST hPAB β重组质粒经酶切可得到约 2 30bp的片段 ,与预期大小相符 ,测序结果表明其序列正确 ;构建的pQE32 CP hPAB β重组表达质粒酶切亦可切出 2 30bp的片段 ,测序结果表明序列和阅读框均正确 ;重组表达质粒在大肠杆菌中能表达出Mr约2 7× 10 3 大小的蛋白 ,表达量约占细菌总蛋白的 4 3% ,该融合蛋白以包涵体形式存在 ,通过亲和层析可获得该蛋白 ,纯度为 80 4 % ,该融合蛋白经羟胺裂解 1h即可得到与合成肽大小相符的小肽。结论 本研究成功构建了含hPAB β重组质粒的工程菌 ,为进一步研究和大量制备hPAB β创造了前提。

Objective To construct the recombinant plasmid with a human peptide antibiotic hPAB-β gene and to make it expressed in E. coli. Methods To replace the CNBr cleavage site in plasmid pFAST-hPAB-β (CNBr), a pair of primers containing the hydroxylamine cleavage site were designed, and the amplified PCR fragments were cloned into pFAST-HTa plasmid to produce pFAST-hPAB-β (HA), which was then transformed into E. coli DH10B. The constructed plasmid was identified by Ehe Ⅰ/Hind Ⅲ digestion and direct DNA sequencing. An Ehe Ⅰ/Hind Ⅲ digested fragment from pFAST-hPAB-β (HA) was subcloned into pQE32-CP to construct pQE32-CP-hPAB-β, which was transformed into E. coli JM109. The bacteria containing the expression plasmid were induced to express the fusion protein by IPTG. SDS-PAGE was carried out to analyze the molecular weight, expression quantity and expression form of the target fusion protein. After captured by Ni-NTA affinity column, the fusion protein was subjected to hydroxylamine cleavage analysis. Results An expected 230bp fragment was obtained by digesting pFAST-hPAB-β with Ehe Ⅰ/Hind Ⅲ. After this fragment was cloned into pQE32-CP, the recombinant plasmid was confirmed to contain the correct target sequence by DNA sequencing. The recombinant plasmid pQE32-CP-hPAB-β could express a desired protein with a relative molecular weight about 27kD, and its expression level reached 43 percent of the total bacterial proteins. The inclusion bodies were lysed by 8mol/L urea, and the fusion protein could then be captured by Ni-NTA column and cleaved by 2mol/L hydroxylamine at pH9.0. Conclusion The recombinant plasmid pQE32-CP-hPAB-β has been successfully constructed, and it can express the desired hPAB-β fusion protein in E. coli JM109 at high level. These results provide the foundation for future research.