Effects of Carbon Source on Expression of F(o) Genes and on the Stoichiometry of the c Subunit in the F(1)F(o) ATPase of Escherichia coli

Expression of the genes for the membrane-bound F(o) sector of the Escherichia coli F(1)F(o) proton-translocating ATPase can respond to changes in metabolic conditions, and these changes are reflected in alterations in the subunit stoichiometry of the oligomeric F(o) proton channel. Transcriptional and translational lacZ fusions to the promoter and to two F(o) genes show that, during growth on the nonfermentable carbon source succinate, transcription of the operon and translation of uncB, encoding the a subunit of F(o), are higher than during growth on glucose. In contrast, translation of the uncE gene, encoding the c subunit of F(o), is higher during growth on glucose than during growth on succinate. Translation rates of both uncB and uncE change as culture density increases, but transcription rates do not. Quantitation of the c stoichiometry shows that more c subunits are assembled into the F(1)F(o) ATPase in cells grown on glucose than in cells grown on succinate. E. coli therefore appears to have a mechanism for regulating the composition and, presumably, the function of the ATPase in response to metabolic circumstances.