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Journal of Virology, April 1999, p. 2909-2915, Vol. 73, No. 4
Department of Biological Sciences,
Received 22 April 1998/Accepted 4 January 1999
Hepatitis G virus (HGV) nonstructural protein 3 (NS3) contains
amino acid sequence motifs typical of ATPase and RNA helicase proteins.
In order to examine the RNA helicase activity of the HGV NS3 protein,
the NS3 region (amino acids 904 to 1580) was fused with maltose-binding
protein (MBP), and the fusion protein was expressed in
Escherichia coli and purified with amylose resin and
anion-exchange chromatography. The purified MBP-HGV/NS3 protein possessed RNA-stimulated ATPase and RNA helicase activities.
Characterization of the ATPase and RNA helicase activities of
MBP-HGV/NS3 showed that the optimal reaction conditions were similar to
those of other Flaviviridae viral NS3 proteins. However,
the kinetic analysis of NTPase activity showed that the MBP-HGV/NS3
protein had several unique properties compared to the other
Flaviviridae NS3 proteins. The HGV NS3 helicase unwinds
RNA-RNA duplexes in a 3'-to-5' direction and can unwind RNA-DNA
heteroduplexes and DNA-DNA duplexes as well. In a gel retardation
assay, the MBP-HGV/NS3 helicase bound to RNA, RNA/DNA, and DNA duplexes
with 5' and 3' overhangs but not to blunt-ended RNA duplexes. We also
found that the conserved motif VI was important for RNA binding.
Further deletion mapping showed that the RNA binding domain was located
between residues 1383 and 1395, QRRGRTGRGRSGR. Our data showed that the
MBP-HCV/NS3 protein also contains the RNA binding domain in the similar domain.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
RNA-Stimulated ATPase and RNA Helicase Activities
and RNA Binding Domain of Hepatitis G Virus Nonstructural
Protein 3
*
Corresponding author. Mailing address: Department of
Biological Sciences, Korea Advanced Institute of Science and
Technology, Taejon 305-701, Korea. Phone: 82-42-869-2630. Fax:
82-42-869-5630. E-mail: jhchoe{at}sorak.kaist.ac.kr.
Journal of Virology, April 1999, p. 2909-2915, Vol. 73, No. 4
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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