Membrane insertion of gp9-T7 in E. coli K38 and JS7131. Exponentially growing E. coli K38 cells (panel A) and JS7131 (panel B), respectively, containing the plasmid pMSg9-T7 were pulse-labelled with 35S-methionine for 10 min. The cells were converted to spheroplasts and incubated on ice for 1 h either in the presence or absence of 0.5 mg/mL proteinase K. The samples were immunoprecipitated with antiserum to T7 (lanes 1, 2), to GroEL (lanes 3, 4) and to OmpA (lanes 5, 6), respectively, and analysed on SDS PAGE and phosphorimaging. (C) The depletion of YidC in the JS7131 cells grown in M9 medium with 0.2% glucose (glc) was verified by Western blot using an antibody to YidC. As control for the non-depleted conditions, the JS7131 cells were grown in the presence of 0.2% arabinose (ara).