Identification of subunits a, b, and c1 from Acetobacterium woodii Na+-F1F0-ATPase -: Subunits c1, c2, and c3 constitute a mixed c-oligomer

The Na+-F1F0-ATPase operon of Acetobacterium woodii was recently shown to contain, among eleven atp genes, those genes that encode subunit a and b, a gene encoding a 16-kDa proteolipid (subunit c(1)), and two genes encoding 8-kDa proteolipids (subunits c(2) and c(3)). Because subunits a, b, and c(1) were not found in previous enzyme preparations, we re-determined the subunit composition of the enzyme. The genes were overproduced, and specific antibodies were raised. Western blots revealed that subunits a, b, and c(1) are produced and localized in the cytoplasmic membrane. Membrane protein complexes were solubilized by dodecylmaltoside and separated by blue native-polyacrylamide gel electrophoresis, and the ATPase subunits were resolved by SDS-polyacrylamide gel electrophoresis. N-terminal sequence analyses revealed the presence of subunits a, c(2), c(3), b, delta, alpha, gamma, beta, and epsilon. Biochemical and immunological analyses revealed that subunits c(1), c(2), and c(3) are all part of the c-oligomer, the first of a F1F0-ATPase that contains 8- and 16-kDa proteolipids.