In vitro guanylylation of infectious pancreatic necrosis virus polypeptide VP1.
Incubation of purified infectious pancreatic necrosis virus (IPNV) in the presence of [alpha 32P]GTP resulted in the formation of VP1-GMP. The GMP is linked to VP1 by a phosphodiester bond and its formation does not require the presence of divalent cations. In contrast to reovirus guanylyl transferase, the formation of IPNV VP1-GMP is not reversible and the guanylylation reaction is not inhibited by inorganic pyrophosphate. Furthermore, the IPNV VP1-GMP cannot transfer the GMP to an acceptor molecule (such as GTP) indicating that VP1 is not a capping enzyme. Time-course experiments revealed that after the initial guanylylation of VP1 to form VP1-pG, a second GMP is added to form VP1-pGpG, the formation of which is template-dependent. Since VP1 is present in the virion both as a free polypeptide and in a genome-linked form as VPg, and it is also the virion-associated RNA polymerase, the results suggest that VP1 may function as a primer during in vitro RNA synthesis.
Department of Microbiology, College of Biological Sciences, University of Guelph, Ontario, Canada.
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D011756:Diphosphates / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D006157:Guanosine Monophosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D012328:RNA Viruses / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D012694:Serine / Q000032:analysis; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
D011756:Diphosphates; D010710:Phosphates; D012367:RNA, Viral; D014764:Viral Proteins; D012694:Serine; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate; D004229:Dithiothreitol