Hepatitis C virus NS3 RNA helicase activity is modulated by the two domains of NS3 and NS4A

• Published in: Biochemical and biophysical research communications Vol. 317; no. 1; pp. 211 - 217
• Main Authors: Kuang, Wan-Fen, Lin, Yu-Chieh, Jean, François, Huang, Yu-Wen, Tai, Chun-Ling, Chen, Ding-Shinn, Chen, Pei-Jer, Hwang, Lih-Hwa
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23.04.2004
• Subjects: Adenosine Triphosphatases - metabolism; Amino Acid Sequence; Animals; Cells, Cultured; Endopeptidases - metabolism; Gene Expression; HCV; Hepacivirus - enzymology; Hepatitis C virus; NS3; NS4A; Oligopeptides - metabolism; Protease; Protein Binding; Protein Structure, Tertiary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; RNA helicase; RNA Helicases - chemistry; RNA Helicases - genetics; RNA Helicases - metabolism; RNA, Double-Stranded - chemistry; RNA, Double-Stranded - metabolism; Spodoptera - cytology; Spodoptera - metabolism; Spodoptera - virology; Viral Nonstructural Proteins - chemistry; Viral Nonstructural Proteins - genetics; Viral Nonstructural Proteins - metabolism; HCV; Protease; NS4A; NS3; RNA helicase
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2004.03.032

To determine whether the two domains of hepatitis C virus (HCV) NS3 and the NS4A interact with each other to regulate the RNA unwinding activity, this study compares the RNA unwinding, ATPase and RNA binding activities of three forms of NS3 proteins—the NS3H protein, containing only the helicase domain, the full-length NS3 protein, and the NS3–NS4A complex. The results revealed that NS3 displayed the weakest RNA helicase activity, not because it had lower ATPase or RNA binding activity than did NS3H or NS3–NS4A, but because it had the lowest RNA unwinding processivity. A mutant protein, R1487Q, which contained a mutation in the helicase domain, displayed a reduced protease activity as compared to the wild-type NS3–NS4A. Together, these results suggest the existence of interactions between the two domains of NS3 and the NS4A, which regulates the HCV NS3 protease and RNA helicase activities.