Pulse-chase study of wild-type and mutant A subunits in BHK cells. Pulse-chase experiments were performed in a mammalian expression system as described in Materials and Methods. Radiolabeled cell lysates and culture media of cells were taken at various time intervals and immunoprecipitated with an antiserum against the A subunit, followed by electrophoresis on 10% SDS-polyacrylamide gels. Top left, mock; top right, wild-type; bottom left, the 4-bp deletion (4-bp del); bottom right, the Gly562-Arg mutant.