Dissociation of newly synthesized Sendai viral proteins from the cytoplasmic surface of isolated plasma membranes of infected cells.

The interaction of Sendai viral proteins with the membranes of infected cells during budding of progeny virions was studied. BHK cells infected with Sendai virus were labeled with [35S]methionine, and the plasma membranes were purified on polycationic polyacrylamide beads. The isolated membranes were incubated with various agents which perturb protein structure to dissociate viral proteins from the membranes. Incubation of membranes with thiocyanate and guanidine removed both the M and nucleocapsid proteins. Urea (6 M) removed the nucleocapsid proteins but removed M protein only in the presence of 0.1 or 1.0 M KCl. In contrast, high salt concentrations alone eluted only the M protein, leaving the nucleocapsid proteins completely membrane bound. About 65% of the M protein was eluted in the presence of 4 M KCl. The remaining membrane-associated M protein was resistant to further extraction by 4 M KCl. Thus, M protein forms two types of interaction with the membrane, one of them being a more extensive association with the membrane than the other.