Abstract
Site-directed mutagenesis has been used to construct two mutations within the uncE gene, which codes for the c-subunit of the F1F0-ATPase, resulting in the substitution of glycine-27 by leucine and of glycine-32 by leucine. Strains carrying each mutation are unable to grow on minimal medium containing succinate as the sole carbon source and possess an uncoupled growth yield. Membranes prepared from strains carrying each mutation possess low levels of ATPase activity and are proton-impermeable. The c-subunit in each mutant strain appears to assemble into the F0-ATPase and disrupt the normal assembly of the F1-ATPase. The results are discussed in relation to a previously proposed model for the F0 sector [Cox, Fimmel, Gibson & Hatch (1986) Biochim. Biophys. Acta 849, 62-69].