PMID:8970970

Citation	Tai, CL, Chi, WK, Chen, DS and Hwang, LH (1996) The helicase activity associated with hepatitis C virus nonstructural protein 3 (NS3). J. Virol. 70:8477-84
Abstract	To assess the RNA helicase activity of hepatitis C virus (HCV) nonstructural protein 3 (NS3), a polypeptide encompassing amino acids 1175 to 1657, which cover only the putative helicase domain, was expressed in Escherichia coli by a pET expression vector. The protein was purified to near homogeneity and assayed for RNA helicase activity in vitro with double-stranded RNA substrates prepared from a multiple cloning sequence and an HCV 5' nontranslated region (5'-NTR) or 3'-NTR. The enzyme acted successfully on substrates containing both 5' and 3' single-stranded regions (standard) or on substrates containing only the 3' single-stranded regions (3'/3') but failed to act on substrates containing only the 5' single-stranded regions (5'/5') or on substrates lacking the single-stranded regions (blunt). These results thus suggest 3' to 5' directionality for HCV RNA helicase activity. However, a 5'/5' substrate derived from the HCV 5'-NTR was also partially unwound by the enzyme, possibly because of unique properties inherent in the 5' single-stranded regions. Gel mobility shift analyses demonstrated that the HCV NS3 helicase could bind to either 5'- or 3'-tailed substrates but not to substrates lacking a single-stranded region, indicating that the polarity of the RNA strand to which the helicase bound was a more important enzymatic activity determinant. In addition to double-stranded RNA substrates, HCV NS3 helicase activity could displace both RNA and DNA oligonucleotides on a DNA template, suggesting that HCV NS3 too was disposed to DNA helicase activity. This study also demonstrated that RNA helicase activity was dramatically inhibited by the single-stranded polynucleotides. Taken altogether, our results indicate that the HCV NS3 helicase is unique among the RNA helicases characterized so far.
Links	PubMed PMC190938
Keywords	Animals; Enzyme Inhibitors/pharmacology; Escherichia coli/metabolism; Hepacivirus/enzymology; Hepacivirus/genetics; Humans; Poly A/pharmacology; Poly G/pharmacology; Poly U/pharmacology; RNA Helicases; RNA Nucleotidyltransferases/antagonists & inhibitors; RNA Nucleotidyltransferases/genetics; RNA Nucleotidyltransferases/metabolism; Rabbits; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Substrate Specificity; Viral Nonstructural Proteins/antagonists & inhibitors; Viral Nonstructural Proteins/genetics; Viral Nonstructural Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HCVJA:POLG		GO:0003724: RNA helicase activity	ECO:0000314:		F		Fig. 3 shows the optimizing reaction conditions for HCV NS3 RNA helicase	complete CACAO 2546
HCVJA:POLG	enables	GO:0003724: RNA helicase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

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