SecA and liposomes alone are capable for promoting ion channel activity in the oocytes. A, additional SecA and ATP-Mg2+ were required for achieving optimal channel activity with liposomes than BA13 membranes containing SecYEG. B, additional SecA is needed for channel activity with SecA-liposomes (■) as compared with BA13 with SecYEG (●). C, homologous SecAs but not non-functional E. coli SecAs can promote the ion channel activity in the oocytes. Various SecAs, 120 ng each, liposomes mixtures were injected together with proOmpA, ATP, and Mg2+ into oocytes. Ec: E. coli, EcSecA-SecA, EcSecAL43P, EcSecAR509K; Pa: Pseudomonas aeruginosa PAO1; Bs: Bacillus subtilis 168.