title: Hepatitis C virus NS3 ATPases/helicases from different genotypes exhibit variations in enzymatic properties.
abstract: The NS3 ATPase/helicase was isolated and characterized from three different infectious clones of hepatitis C virus (HCV). One helicase was from a genotype that normally responds to therapy (Hel-2a), and the other two were from more resistant genotypes, 1a (Hel-1a) and 1b (Hel-1b). Although the differences among these helicases are generally minor, all three enzymes have distinct properties. Hel-1a is less selective for nucleoside triphosphates, Hel-1b hydrolyzes nucleoside triphosphates less rapidly, and Hel-2a unwinds DNA more rapidly and binds DNA more tightly than the other two enzymes. Unlike related proteins, different nucleic acid sequences stimulate ATP hydrolysis by HCV helicase at different maximum rates and with different apparent efficiencies. This nucleic acid stimulation profile is conserved among the enzymes, but it does not result entirely from differential DNA-binding affinities. Although the amino acid sequences of the three proteins differ by up to 15%, one variant amino acid that is critical for helicase action was identified. NS3 residue 450 is a threonine in Hel-1a and Hel-1b and is an isoleucine in Hel-2a. A mutant Hel-1a with an isoleucine substituted for threonine 450 unwinds DNA more rapidly and binds DNA more tightly than the parent protein.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York 10595, USA.
authors.forename: Angela M I
authors.initials: AM
authors.lastname: Lam
authors.forename: David
authors.initials: D
authors.lastname: Keeney
authors.forename: Patrick Q
authors.initials: PQ
authors.lastname: Eckert
authors.forename: David N
authors.initials: DN
authors.lastname: Frick
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D019943:Amino Acid Substitution; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D014644:Genetic Variation; D005838:Genotype; D016174:Hepacivirus / Q000201:enzymology* / Q000235:genetics*; D006526:Hepatitis C / Q000188:drug therapy / Q000821:virology; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D020365:RNA Helicases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D004279:DNA, Viral; D020365:RNA Helicases; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases