【目的】圣路易斯脑炎病毒(St. Louis encephalitis virus,SLEV)属于黄病毒科,是一种单股正链RNA病毒。黄病毒编码的非结构蛋白NS3在病毒复制以及多聚蛋白加工过程中起着重要作用,NS2B是其发挥作用的重要辅助因子。因此,NS2B-NS3蛋白酶...【目的】圣路易斯脑炎病毒(St. Louis encephalitis virus,SLEV)属于黄病毒科,是一种单股正链RNA病毒。黄病毒编码的非结构蛋白NS3在病毒复制以及多聚蛋白加工过程中起着重要作用,NS2B是其发挥作用的重要辅助因子。因此,NS2B-NS3蛋白酶复合物是抗病毒药物的重要靶标。本研究旨在构建SLEV NS2B-NS3蛋白酶的原核表达系统并建立其抑制剂的高通量筛选方法,从而发现其小分子抑制剂。【方法】通过PCR扩增SLEVNS2B-NS3蛋白的编码区,构建原核表达质粒;在大肠杆菌BL21(DE3)中,经异丙基硫代半乳糖苷(Isopropyl β-D-thiogalactoside)诱导得到可溶性的NS2B-NS3蛋白,并用镍亲和层析方法进行纯化;基于荧光共振能量转移(Fluorescence resonance energy transfer)技术检测NS2B-NS3蛋白酶活性,建立其抑制剂的高通量筛选平台。【结果】SLEV NS2B-NS3蛋白酶纯化程度高达95%以上,基于酶活测定的抑制剂筛选平台准确可行。对700多个上市药物进行筛选后,发现原花青素对SLEVNS2B-NS3蛋白酶具有明显的抑制活性。【结论】本研究为SLEVNS2B-NS3蛋白酶抑制剂提供了一种操作方便、高通量的筛选方法,并首次发现了原花青素具有抑制SLEV NS2B-NS3蛋白酶活性的功能,可以作为治疗SLEV感染的潜在靶向药物。展开更多
AIM: To establish a simple and convenient assay in vitro for the Hepatitis C virus NS3 serine protease based on the recombinant protease and substrate, and to evaluate its feasibility in screening the enzyme inhibitor...AIM: To establish a simple and convenient assay in vitro for the Hepatitis C virus NS3 serine protease based on the recombinant protease and substrate, and to evaluate its feasibility in screening the enzyme inhibitors. METHODS: Based on the crystallographic structure of hepatitis C virus (HCV) serine protease, a novel single-chain serine protease was designed, in which the central sequence of cofactor NS4A was linked to the N-terminus of NS3 serine protease domain via a flexible linker GSGS. The fusion gene was obtained by two-step PCR that was carried out with three primers and then cloned into the prokaryotic expression vector pQE30, and the recombinant clone was verified by DNA sequencing. The single-chain recombinant protease was expressed when the E.coliwas induced with IPTG and the expression conditions were optimized to produce large amount of soluble protease. The recombinant substrate NS5ab that covers the cleavage point NS5A/B was also expressed in E.coli. Both of the protease and substrate were purified by using Ni-NTA agarose metal affinity resin, then they were mixed together in a specific buffer, and the mixture was analyzed by SDS-PAGE. The cleavage system was used to evaluate some compounds for their inhibitory activity on serine protease.RESULTS: The single-chain recombinant protease was overexpressed as soluble protein when the E. coliwas induced at a low dosage of IPTG (0.2 mM) and cultured at a low temperature (15℃). The protease was purified by using Ni-NTA agarose metal affinity resin (the purity is over 95 %).The recombinant substrate NS5ab was expressed in an insoluble form and could refold successfully after purification and dialysis. A simple and convenient assay in vitro was established, in which the purified single-chain serine protease could cleave the recombinant substrate NS5ab into two fragments that were visualized by SDS-PAGE. PMSF had an effect on inhibiting activity of serine protease, while EDTA had not.CONCLUSION: A simple and convenient assayin vitro for hepatitis C virus NS3 serine protease is based on recombinant substrate NS5ab and single-chain serine protease. This assay can be used in screening of enzyme inhibitors.展开更多
AIM: To produce the recombinant NS3 protease of hepatitis C virus with enzymatic activity in insect cells.METHODS: The gene of HCV serine proteinase domain which encodes 181 amino acids was inserted into pFastBacHTc a...AIM: To produce the recombinant NS3 protease of hepatitis C virus with enzymatic activity in insect cells.METHODS: The gene of HCV serine proteinase domain which encodes 181 amino acids was inserted into pFastBacHTc and the recombinant plasmid pFBCNS3N was transformed into DH10Bac competent cells for transposition.After the recombinant bacmids had been determined to be correct by both blue-white colonies and PCR analysis, the isolated bacmid DNAs were transfected into Sf9 insect cells.The bacmids DNA was verified to replicate in insect cells and packaged into baculovirus particles via PCR and electronic microscopic analysis. The insect cells infected with recombinant baculovirus were determined by SDS-PAGE and Western-blot assays. The recombinant protein was soluted in N-lauryl sarcosine sodium (NLS) and purifed by metalchelated-affinity chromatography, then the antigenicity of recombinant protease was determined by enzyme-linked immunoabsorbant assay and its enzymatic activity was detected.RESULTS: The HCV NS3 protease domain was expressed in insect cells at high level and it was partially solved in NLS.Totally 0.2 mg recombinant serine proteinase domain with high purity was obtained by metal-chelated-affinity chromatography from 5×107 cells, and both antigenicity and specificity of the protein were evaluated to be high when used as antigen to detect hepatitis C patients′ sera in indirect ELISA format. In vitro cleavage assay corroborated its enzymatic activity.CONCLUSION: The recombinant HCV NS3 proteinase expressed by insect cells is a membrane-binding protein with good antigenicity and enzymatic activity.展开更多
基金the National Natural Science Foundation of China,No.39630020
文摘AIM: To establish a simple and convenient assay in vitro for the Hepatitis C virus NS3 serine protease based on the recombinant protease and substrate, and to evaluate its feasibility in screening the enzyme inhibitors. METHODS: Based on the crystallographic structure of hepatitis C virus (HCV) serine protease, a novel single-chain serine protease was designed, in which the central sequence of cofactor NS4A was linked to the N-terminus of NS3 serine protease domain via a flexible linker GSGS. The fusion gene was obtained by two-step PCR that was carried out with three primers and then cloned into the prokaryotic expression vector pQE30, and the recombinant clone was verified by DNA sequencing. The single-chain recombinant protease was expressed when the E.coliwas induced with IPTG and the expression conditions were optimized to produce large amount of soluble protease. The recombinant substrate NS5ab that covers the cleavage point NS5A/B was also expressed in E.coli. Both of the protease and substrate were purified by using Ni-NTA agarose metal affinity resin, then they were mixed together in a specific buffer, and the mixture was analyzed by SDS-PAGE. The cleavage system was used to evaluate some compounds for their inhibitory activity on serine protease.RESULTS: The single-chain recombinant protease was overexpressed as soluble protein when the E. coliwas induced at a low dosage of IPTG (0.2 mM) and cultured at a low temperature (15℃). The protease was purified by using Ni-NTA agarose metal affinity resin (the purity is over 95 %).The recombinant substrate NS5ab was expressed in an insoluble form and could refold successfully after purification and dialysis. A simple and convenient assay in vitro was established, in which the purified single-chain serine protease could cleave the recombinant substrate NS5ab into two fragments that were visualized by SDS-PAGE. PMSF had an effect on inhibiting activity of serine protease, while EDTA had not.CONCLUSION: A simple and convenient assayin vitro for hepatitis C virus NS3 serine protease is based on recombinant substrate NS5ab and single-chain serine protease. This assay can be used in screening of enzyme inhibitors.
基金the National Natural Science Foundation of China,No.39630020
文摘AIM: To produce the recombinant NS3 protease of hepatitis C virus with enzymatic activity in insect cells.METHODS: The gene of HCV serine proteinase domain which encodes 181 amino acids was inserted into pFastBacHTc and the recombinant plasmid pFBCNS3N was transformed into DH10Bac competent cells for transposition.After the recombinant bacmids had been determined to be correct by both blue-white colonies and PCR analysis, the isolated bacmid DNAs were transfected into Sf9 insect cells.The bacmids DNA was verified to replicate in insect cells and packaged into baculovirus particles via PCR and electronic microscopic analysis. The insect cells infected with recombinant baculovirus were determined by SDS-PAGE and Western-blot assays. The recombinant protein was soluted in N-lauryl sarcosine sodium (NLS) and purifed by metalchelated-affinity chromatography, then the antigenicity of recombinant protease was determined by enzyme-linked immunoabsorbant assay and its enzymatic activity was detected.RESULTS: The HCV NS3 protease domain was expressed in insect cells at high level and it was partially solved in NLS.Totally 0.2 mg recombinant serine proteinase domain with high purity was obtained by metal-chelated-affinity chromatography from 5×107 cells, and both antigenicity and specificity of the protein were evaluated to be high when used as antigen to detect hepatitis C patients′ sera in indirect ELISA format. In vitro cleavage assay corroborated its enzymatic activity.CONCLUSION: The recombinant HCV NS3 proteinase expressed by insect cells is a membrane-binding protein with good antigenicity and enzymatic activity.
