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Potyviral NIa Proteinase, a Proteinase with Novel Deoxyribonuclease Activity

Anindya, Roy and Savithri, Handanahal S (2004) Potyviral NIa Proteinase, a Proteinase with Novel Deoxyribonuclease Activity. In: Journal of Biological Chemistry, 279 (31). pp. 32159-32169.

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The NIa proteinase from Pepper vein banding virus (PVBV) is a sequence specific proteinase required for processing of viral poly-protein in the cytoplasm. It accumulates in the nucleus of the infected plant cell and forms inclusion bodies. The function of this protein in the nucleus is not clear. The purified recombinant NIa proteinase was active and the mutation of the catalytic residues H46, D81 and C151 resulted in complete loss of activity. Interestingly the PVBV NIa proteinase exhibited hitherto unidentified activity namely non-specific dsDNA degradation. This deoxyribonuclease (DNase) activity of the NIa proteinase showed an absolute requirement for Mg$^{\math{2+}}$ . Site-specific mutational analysis showed that of the three catalytic residues, D81 was the crucial residue for DNase activity. Mutation of H46 and C151 had no effect on the DNase activity, whereas mutant D81N was partially active and D81G was completely inactive. Based on the kinetic analysis and molecular modeling, a metal ion dependent catalysis similar to that observed in other non-specific DNases is proposed. Similar results were obtained with GST-fused PVBV NIa proteinase and Tobacco etch virus NIa proteinase, confirming that the DNase function is an intrinsic property of potyviral NIa proteinase. The NIa protein present in the infected plant nuclear extract also showed the proteinase and the DNase activities suggesting that PVBV NIa protein which accumulates in the nucleus late in the infection cycle might serve to degrade the host DNA. Thus the dual function of the NIa proteinase could play an important role in the life cycle of the virus.

Item Type: Journal Article
Publication: Journal of Biological Chemistry
Publisher: The American Society for Biochemistry and Molecular Biology
Additional Information: The copyright of this article belongs to The American Society for Biochemistry and Molecular Biology.
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 28 Oct 2004
Last Modified: 17 Jan 2012 06:11
URI: http://eprints.iisc.ac.in/id/eprint/2183

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