Nucleotide Phosphotransferase, Nucleotide Kinase and Inorganic Pyrophosphatase Activities of Killer Virions of Yeast

The intracellular killer virions of yeast co-purify with an RNA polymerase activity which catalyzes the synthesis of full-length transcripts of the two viral genomic double-stranded RNA segments. This polymerase utilizes ribonucleoside diphosphates or triphosphates as substrates. The virions have other associated nucleotide-metabolizing enzyme activities, including nucleoside diphosphate kinase, adenosine monophosphate kinase, and nucleoside triphosphate phosphotransferase, an activity which catalyzes the exchange of gamma-phosphate from any ribonucleoside triphosphate with any ribonucleoside or deoxyribonucleoside triphosphate. The purified virions also contain an inorganic pyrophosphatase activity. These enzymes may allow the virus to utilize nucleotide pools distinct from those utilized in host cell transcription.