title: A novel recombinant single-chain hepatitis C virus NS3-NS4A protein with improved helicase activity.
abstract: Hepatitis C virus (HCV) nonstructural protein 3 (NS3) has been shown to possess protease and helicase activities and has also been demonstrated to spontaneously associate with nonstructural protein NS4A (NS4A) to form a stable complex. Previous attempts to produce the NS3/NS4A complex in recombinant baculovirus resulted in a protein complex that aggregated and precipitated in the absence of nonionic detergent and high salt. A single-chain form of the NS3/NS4A complex (His-NS4A21-32-GSGS-NS3-631) was constructed in which the NS4A core peptide is fused to the N-terminus of the NS3 protease domain as previously described (Taremi et al., 1998). This protein contains a histidine tagged NS4A peptide (a.a. 21-32) fused to the full-length NS3 (a.a. 3-631) through a flexible tetra amino acid linker. The recombinant protein was expressed to high levels in Escherichia coli, purified to homogeneity, and examined for NTPase, nucleic acid unwinding, and proteolytic activities. The single-chain recombinant NS3-NS4A protein possesses physiological properties equivalent to those of the NS3/NS4A complex except that this novel construct is stable, soluble and sixfold to sevenfold more active in unwinding duplex RNA. Comparison of the helicase activity of the single-chain recombinant NS3-NS4A with that of the full-length NS3 (without NS4A) and that of the helicase domain alone suggested that the presence of the protease domain and at least the NS4A core peptide are required for optimal unwinding activity.
authors.affiliation: Department of Antiviral Therapy, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA. anita.howe@spcorp.com
authors.forename: A Y
authors.initials: AY
authors.lastname: Howe
authors.forename: R
authors.initials: R
authors.lastname: Chase
authors.forename: S S
authors.initials: SS
authors.lastname: Taremi
authors.forename: C
authors.initials: C
authors.lastname: Risano
authors.forename: B
authors.initials: B
authors.lastname: Beyer
authors.forename: B
authors.initials: B
authors.lastname: Malcolm
authors.forename: J Y
authors.initials: JY
authors.lastname: Lau
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D016174:Hepacivirus / Q000737:chemistry* / Q000201:enzymology; D006868:Hydrolysis; D008969:Molecular Sequence Data; D020365:RNA Helicases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000378:metabolism; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D017931:DNA Primers; D020365:RNA Helicases; D011994:Recombinant Proteins; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C093542:NS4 protein, hepatitis C virus