title: A central region in the hepatitis C virus NS4A protein allows formation of an active NS3-NS4A serine proteinase complex in vivo and in vitro.
abstract: A virus-encoded serine proteinase mediates four site-specific cleavages in the hepatitis C virus polyprotein. In addition to the catalytic domain, which is located in the N-terminal one-third of nonstructural protein NS3, the 54-residue NS4A protein is required for cleavage at some but not all sites. Here, we provide evidence for a non-ionic detergent-stable interaction between NS4A and the NS3 serine proteinase domain and demonstrate that the central region of NS4A plays a key role in NS4A-dependent processing. Hydrophobic residues, in particular Ile-29, were shown to be important for NS4A activity, and a synthetic peptide, spanning NS4A residues 22 to 34, could substitute for intact NS4A in a cell-free trans cleavage assay. Furthermore, NS4A mutations, which abolished or inhibited processing, correlated with destabilization of the NS3-NS4A complex. These results suggest that a stable interaction exists between the central region of NS4A and the NS3 catalytic domain which is required for NS4A-dependent processing. Since NS4A is required for processing at certain serine proteinase-dependent cleavage sites, this interaction may represent a new target for development of antiviral compounds.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA.
authors.forename: C
authors.initials: C
authors.lastname: Lin
authors.forename: J A
authors.initials: JA
authors.lastname: Thomson
authors.forename: C M
authors.initials: CM
authors.lastname: Rice
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D009154:Mutation; D017830:Octoxynol / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000502:physiology; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D017830:Octoxynol; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases