SECE-DEPLETED MEMBRANES OF ESCHERICHIA-COLI ARE ACTIVE - SECE IS NOT OBLIGATORILY REQUIRED FOR THE IN-VITRO TRANSLOCATION OF CERTAIN PROTEIN PRECURSORS

Membrane vesicles were prepared from Escherichia coil cells in which S ecE was depleted to 2% of wild-type membranes. SecE depletion had plei otropic effects; SecD, SecF, SecG, and SecY were decreased 4-6-fold, w hereas SecA was increased about 16-fold over that of wild-type membran es. These membranes were substantially active in the in vitro transloc ation of proOmpA, which was mediated by the SecA pathway since it was inhibited by azide. Similar substantial translocation activities were observed for proLamB and proLpp in the SecE depleted membranes. Howeve r, the translocation of proPhoA was more severely impaired. These data indicate that SecE may enhance but is not obligatorily required for t he translocation of at least certain precursors, and suggest that the effects of the SecE depletion on protein translocation may be precurso r-dependent.