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J. Virol., 03 1995, 1720-1726, Vol 69, No. 3
P Warrener and MS Collett
The pestivirus bovine viral diarrhea virus (BVDV) p80 protein (referred to
here as the NS3 protein) contains amino acid sequence motifs predictive of
three enzymatic activities: serine proteinase, nucleoside triphosphatase,
and RNA helicase. We have previously demonstrated that the former two
enzymatic activities are associated with this protein. Here, we show that a
purified recombinant BVDV NS3 protein derived from baculovirus-infected
insect cells possesses RNA helicase activity. BVDV NS3 RNA helicase
activity was specifically inhibited by monoclonal antibodies to the p80
protein. The activity was dependent on the presence of nucleoside
triphosphate and divalent cation, with a preference for ATP and Mn2+.
Hydrolysis of the nucleoside triphosphate was necessary for strand
displacement. The helicase activity required substrates with an
un-base-paired region on the template strand 3' of the duplex region. As
few as three un-base-paired nucleotides were sufficient for efficient
oligonucleotide displacement. However, the enzyme did not act on substrates
having a single-stranded region only to the 5' end of the duplex or on
substrates lacking single-stranded regions altogether (blunt-ended duplex
substrates), suggesting that the directionality of the BVDV RNA helicase
was 3' to 5' with respect to the template strand. The BVDV helicase
activity was able to displace both RNA and DNA oligonucleotides from RNA
template strands but was unable to release oligonucleotides from DNA
templates. The possible role of this activity in pestivirus replication is
discussed.
Copyright © 1995, American Society for Microbiology
Pestivirus NS3 (p80) protein possesses RNA helicase activity
PathoGenesis Corporation, Seattle, Washington 98119.
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