Structural and nonstructural proteins of a rabbit parvovirus

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Abstract
The structural and nonstructural polypeptides of a rabbit parvovirus (RPV) (F-7-9 strain) were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The virion contained three polypeptide components, A (molecular weight, 96,000), B (85,000), and C (75,000). A part of the polypeptide C was cleaved into the smaller-molecular-weight polypeptide C' by proteolysis during purification steps. The major polypeptide C together with C' constituted about 87% of the total viral proteins, and the minor polypeptides, A and B, constituted 4 and 9%, respectively. The structural polypeptides of empty particles were similar in size and composition to those of the virion, but the content of the C' polypeptide was very low. When rabbit kidney cell cultures were infected with RPV, the C polypeptide was detected as early as 15 h postinfection, whereas A and B were first demonstrated at 18 h. The C' polypeptide was not detected for 44 h. In addition to the three structural polypeptides, at least three nonstructural polypeptides, E, F, and G, were demonstrated in the RPV-infected cells. Polypeptide E (molecular weight, 49,000), detected mostly in cytoplasm, seemed to be a cellular protein. The F (25,000) and G (22,000) polypeptides seemed to be virus-coded proteins since they were precipitated with the anti-RPV rabbit immunoglobulin. According to partial proteolysis and peptide mapping, the F and G polypeptides shared the same peptide components.