Optimization of expression conditions of dengue virus NS2B-NS3 protease in E.coli and determination of enzyme activity / 中国生物制品学杂志

ABSTRACT

@#Objective To express dengue virus(DENV)NS2B-NS3 protease in E.coli,optimize the expression conditions and determine the enzyme activity,so as to lay a foundation of screening and discovering of lead compounds targeting DENV.Methods Codon-optimized NS2B-NS3 gene was inserted into pET-28a vector to construct recombinant prokaryotic expression plasmid pET-28a-NS2B-NS3,which was transformed E.coli Rosetta(DE3)competent cells and induced by IPTG to express NS2B-NS3 protease. The optimal expression conditions of NS2B-NS3 protease in E.coli were determined by optimizing induction length,induction temperature and IPTG concentration. NS2B-NS3 protease was isolated and purified by HisTrap~(TM) affinity chromatography column and measured for the protease activity by fluorescence resonance energy transfer(FRET)assay.Results The recombinant prokaryotic expression plasmid pET-28a-NS2B-NS3 was constructed correctly as identified by restriction analysis(NheⅠ/XhoⅠ)and sequencing. The optimal expression conditions of NS2BNS3 protease in E.coli were as followsinduction temperature of 20 ℃,induction length of 10 h and IPTG concentration of0. 2 mmol/L. The purified NS2B-NS3 protease showed a purity of more than 90% with a exhibited a of 20 mg/L,which bound to mouse monoclonal antibody against His-tag specifically and had good hydrolytic activity with a specific activity of 16. 111 U/mg,a K_m of 16. 46 μmol/L and a k_(cat) of 0. 028/s.Conclusion DENV NS2B-NS3 protease with high purity and activity was successfully prepared,which laid an experimental foundation of the establishment of high-throughput screening model for inhibitors targeting NS2B-NS3 protease.