Phosphorylated proteins in cauliflower mosaic virus.

Autoradiography of dodecyl sulfate-impregnated polyacrylamide gels after electrophoresis of the proteins from 32P-labeled cauliflower mosaic virus (CaMV) showed that two of the structural proteins were phosphorylated. These two proteins of 44 and 58 kilodaltons (kd) occur as minor components with some strains of the virus, but with other virus strains under particular conditions the 44-kd protein appears as a major component of the virion. The site of phosphorylation was found to be phosphoserine and phosphothreonine. It is suggested from these results that the 58-kd protein may be the primary translation product of the coat protein gene of CaMV and that the 44-kd and other lower molecular weight forms of the coat protein are derived from this polypeptide by proteolysis.