The structural polypeptides of aphthovirus are phosphoproteins

Analysis of aphthovirus A12, strain 119ab, grown in the presence of inorganic 32P revealed that two of the major viral polypeptides, VP4 and trypsin-sensitive protein VP3, were highly phosphorylated. The other major polypeptides, VP1 and VP2, were also phosphorylated but to a much lesser extent. Polypeptides VP0 and P56, of which there are approximately one of two copies per aphthovirion, were also labeled with 32P. Phosphoserine and phosphothreonine appeared to be the amino acids labeled with 32P.