We have expressed the putative RNA-dependent RNA polymerase encoded by the potyvirus tobacco vein mottling virus (TVMV) in Escherichia coli as a glutathione S-transferase fusion protein. As prepared, the fusion protein possessed the poly(U) polymerase activity that is a hallmark of other picornavirus-encoded polymerases. In addition, this protein was able to utilize full-length TVMV RNA as a template for RNA synthesis. A fusion protein containing a mutation in the highly conserved GDD motif of the polymerase (GDD → ADD) possessed 7% of the activity of the wild type. Our results confirm that the presumed polymerase encoded by TVMV is in fact an RNA-dependent RNA polymerase and that the GDD motif so widely seen in viral polymerases has an important function in the TVMV protein.
|Number of pages||6|
|State||Published - Dec 1 1996|
Bibliographical noteFunding Information:
We thank Carol Von Lanken for excellent technical assistance in this work, and Jaydip Das Gupta for the gift of purified pea poly(A) polymerase. We are grateful to John Shaw for helpful suggestions. This work was supported by USDA NRI Competitive Grant 94-37303-0470.
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