title: Mechanistic studies of electrophilic protease inhibitors of full length hepatic C virus (HCV) NS3.
abstract: The inhibition mechanism of electrophilic peptide-based protease inhibitors of full-length hepatitis C virus (HCV) NS3 has been investigated by determining the K(i)-values for a series of compounds differing in the electrophilicity and acidity of the C-terminal residue at pH-values above and below the pK(a) of the catalytic histidine (6.85) and at two different ionic strengths. Electrophilic compounds with a pentafluoroethyl ketone group showed stronger inhibition at pH 8 than pH 6, as expected for a mechanism requiring an unprotonated catalytic histidine. However, the difference was only significant at high ionic strength. In contrast, electrophilic compounds with an acidic C-terminal group or a cyclic P1 residue showed a lower inhibitory effect at pH 8 than at pH 6, inconsistent with a mechanism-based inhibition. Moreover, all electrophilic compounds had an unexpectedly strong inhibition at pH 6, when mechanism-based inhibition is unlikely. The results suggest that for some of the electrophilic compounds the reactive group may not be properly positioned in the active site and that binding of these inhibitors is a result of non-covalent interactions. The nature of these interactions is discussed.
authors.affiliation: Department of Biochemistry and Organic Chemistry, Uppsala University, BMC, Box 576, Uppsala SE-751 23, Sweden.
authors.forename: Anton
authors.initials: A
authors.lastname: Poliakov
authors.forename: Anja
authors.initials: A
authors.lastname: Sandström
authors.forename: Eva
authors.initials: E
authors.lastname: Akerblom
authors.forename: U Helena
authors.initials: UH
authors.lastname: Danielson
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D012965:Sodium Chloride / Q000737:chemistry; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D000998:Antiviral Agents; D009842:Oligopeptides; D011480:Protease Inhibitors; D012965:Sodium Chloride; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases