title: Critical point mutations for hepatitis C virus NS3 proteinase.
abstract: The hepatitis C virus NS3 proteinase plays an essential role in processing of HCV nonstructural precursor polyprotein. To detect its processing activity, we developed a simple trans-cleavage assay. Two recombinant plasmids expressing the NS3 proteinase region and a chimeric substrate polyprotein containing the NS5A/5B cleavage site between maltose binding protein and protein A were co-introduced into Escherichia coli cells. The proteinase processed the substrate at the single site during their polyprotein expression. Deletion analysis indicated that the functionally minimal domain of the NS3 proteinase was composed of 146 amino acids, 1059 to 1204. We isolated several cDNA clones encoding the functional domain of the NS3 proteinase from the sera of patients chronically infected with HCV and determined their proteinase activity by this trans-cleavage assay. Both active and inactive clones existed in the same patients. Comparative sequence analyses of these clones suggested that certain point mutations seemed to be related to the loss of proteolytic activity. This was confirmed by back mutation experiments. Among the critical mutations, Pro-1168 to Thr and Arg-1135 to Gly were intriguing. These amino acids, which are situated near the oxyanion hole, seem to be essential for maintaining the conformation of the active center of the NS3 proteinase.
authors.affiliation: Molecular Medicine Laboratory, Yokohama Research Center, Mitsubishi Chemical Corp., Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamada
authors.forename: A
authors.initials: A
authors.lastname: Mori
authors.forename: M
authors.initials: M
authors.lastname: Seki
authors.forename: J
authors.initials: J
authors.lastname: Kimura
authors.forename: S
authors.initials: S
authors.lastname: Yuasa
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuura
authors.forename: T
authors.initials: T
authors.lastname: Miyamura
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D016174:Hepacivirus / Q000201:enzymology* / Q000235:genetics; D006526:Hepatitis C / Q000821:virology; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics*; D011392:Proline / Q000235:genetics; D011487:Protein Conformation; D020365:RNA Helicases; D012367:RNA, Viral / Q000097:blood; D016415:Sequence Alignment; D017384:Sequence Deletion; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D001120:Arginine; D018076:DNA, Complementary; D011392:Proline; D020365:RNA Helicases; D012367:RNA, Viral; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C060028:NS3 protein, flavivirus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases