HCV NS5A-B片段的表达及在酶活性研究中的应用

目的：利用原核表达载体pBVIL1，表达丙型肝炎病毒非结构蛋白（NS3）丝氨酸蛋白酶催化底物NS5A—B小分子，为进一步研究蛋白酶活性提供方法学。方法：将PCR合成的NS5A—B（2412—2427aa）基因直接插入高效原核表达载体pBVIL1，融合表达NS5A—B片段．包涵体形式的表达产物用8mol／L脲溶解后，采用离子交换和凝胶过滤两步纯化。利用SDS—PAGE、Western blot和ELISA方法，于37℃酶催化条件下，分析NS5A—B底物的降解活性。结果：（1）构建了pBVIL1／NS5A—B重组质粒，鉴定证明NS5A—B基因片段正确地插入表达载体上：融合蛋白在转化质粒的HB101菌中得到高效表达。分离纯化重组蛋白后浓度可达0．73g／L。（2）在NS3蛋白酶作用不同时间后，用SDS—PAGE和Western blot证实，底物带可被明显降解，ELISA分析也证明，NS5A—B具有酶底物活性。结论：含有酶切位点的NS5A—B融合蛋白可被NS3丝氦酸蛋白酶有效地降解，可用作为NS3蛋白酶的底物，可替代全长NS5A—B和化学合成肽用于酶活性和酶阻断剂的研究

Preparation of recombinant IL-1 fusion protein as the substrate for HCV NS3 serine protease

AIM: To prepare recombinant IL-1 fusion protein as the substrate for the HCV NS3 serine protease. METHODS: NS5A-B gene fragment (2,412-2,427aa) synthesized by PCR was subcloned into prokaryotic expression vector pBVIL1 to fuse with IL-1 gene and the recombinant vector pBVIL1/NS5A-B was transformed into E.coli strain HB101. The fused protein was induced to express at 42degreesCelsius and purified by two-step column chromatography. The proteolysis of the purified IL-1 fusion protein catalyzed by NS3 serine protease was analyzed with SDS-PAGE, Western blot and ELISA. RESULTS: NS5A-B fragment gene was correctly subcloned into pBVIL1 vector and the fusion protein was expressed as inclusion body in transformed HB101 cells. The recombinant fusion protein can be cleaved into smaller fragments by NS3 protease. CONCLUSION: The recombinant fusion protein can be cleaved by NS3 serine protease successfully and specifically, suggesting that it can be used as a surrogate substrate of NS3 serine protease in searching for inhibitors of this protease.