Effect of N,alpha-tosyl-L-phenylalanine chloromethyl ketone on measles virus P and M polypeptides.

Treatment of measles virus-infected cells with 1 mM N,alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) was observed to change the polyacrylamide gel migration of viral polypeptides P and M. Untreated cells contained P as a mixture of P1 (70,000 daltons) and P2 (65,000 daltons) and M as a 38,000-dalton band M1 and a slightly smaller band, M2. TPCK treatment resulted in conversion of P largely to the 65,000-dalton band and of M to M1 and a slightly slower-migrating band. This effect could also be demonstrated by treating homogenates of infected cells with TPCK, and the evidence suggests that the compound reacts directly with the viral P and M polypeptides and thereby changes their gel migration. TPCK also inhibited measles virus-associated protein kinase, and treatment of virion preparations with the compound resulted in a loss of infectivity; however, it was not possible to directly correlate the inhibitory effect on these two biological functions with the change seen in polypeptides P and M.