Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2010
Publication Date: 3/1/2011
Citation: Gladue, D.P., Gavrilov, B.K., Holinka-Patterson, L.G., Fernandez-Sainz, I.J., Vepkhvadze, N.G., Rogers, K., O'Donnell, V., Borca, M.V. 2011. Identification of an NTPase motif in classical swine fever virus NS4B protein. Virology. 411(1):41-49. Interpretive Summary: Classical swine fever (CSF) is a highly contagious and often fatal disease of swine caused by CSF virus (CSFV). The virus in composed, besides its nucleic acids, by structural proteins (SP), which are part of the virus particles itself. Besides the SP, the genome of the virus encodes for the non structural proteins (NSP) which are mainly involved in the process of virus replication. There are ten NSP and the functions of most of them are unclear. In this paper we identify, by genetic analysis first, that one of the NSP, the NS4B, can work facilitating the synthesis of virus nucleic acid during the replication of the virus in the cell. We present data demonstrating experimentally that the isolated NS4B protein plays its role in vitro. We also determined the amino acid residues in the protein that mediate the function. These results have important implications for developing novel antiviral strategies against CSFV that may affect the efficacy of virus replication.
Technical Abstract: Classical swine fever (CSF) is a highly contagious and often fatal disease of swine caused by CSF virus (CSFV), a positive sense single-stranded RNA virus in the genus Pestivirus of the Flaviviridae family. Here, we have identified, within CSFV non-structural (NS) protein NS4B, conserved sequence elements observed in nucleotide-binding motifs (NBM) of enzymes that hydrolyze NTPs. NS4B protein expressed in baculovirus hydrolyzes both ATP and GTP. Substitutions of critical residues within NS4B NBM conserved Walker A and B motifs significantly impair ATPase and GTPase activities of expressed proteins. Similar mutations introduced into the genetic backbone of a full-length DNA copy of CSFV strain Brescia rendered viruses with impaired replicative capabilities, suggesting that this NTPase activity is critical for CSFV life cycle. These results have important implications for developing novel antiviral strategies against CSFV.