Evidence that polyoma polypeptide VP1 is a serine protease.

It has been shown that when purified polyoma (Py) virions are dissociated by incubation in 150 mM NaCl-50 mM Tris-HCl (pH 8.5) containing 1 mM EGTA and 3 mM DTT, two new polypeptides (MW 43.5K and 40K) are produced by proteolysis of virion polypeptide VP1.