Phophorylation of polyoma and SV40 virus proteins.

The polypeptides of polyoma and SV40 virions are phosphorylated. An estimate of the amount of phosphorylation of the major virus capsid protein (VPI) has been made using two-dimensional gel electrophoresis to resolve phosphorylated from non-phosphorylated forms. The results suggest that in both polyoma and SV40 virions about 12% of VPI molecules are phosphorylated. In unassembled VPI molecules immunoprecipitated from extracts of infected cells the proportion is greater, about 33%. The possibility that phosphorylated VPI may form the penton proteins of the virus capsid is discussed.