J774 cells were infected with the indicated strains of L. monocytogenes expressing either wild-type PC-PLC or a PC-PLC propeptide mutant. Pulse-labelled infected cells were perfused with nigericin-supplemented buffer at pH 7.3 or pH 6.5. Radiolabelled PC-PLC was immunoprecipitated from host cell lysates. The secreted protein was detected by autoradiography to determine the efficacy of translocation of PC-PLC at pH 7.3 and of maturation at pH 6.5. The position of a molecular-mass marker in kDa is indicated on the far left-hand side. Positions of the proform and mature form of wild-type PC-PLC are indicated on the far right-hand side. (A) Lanes 1 and 2, HEL-1031; lanes 3 and 4, HEL-1043; lanes 5 and 6, HEL-1046; and lane A 7, DP-L1935. (B) Lanes 1 and 2, HEL-1031; lanes 3 and 4, HEL-1037; lanes 5 and 6, HEL-1223; lanes 7 and 8, HEL-1166; and lanes 9 and 10, HEL-1167.