Sequence of subunit a of the Na+-translocating F1F0-ATPase of Acetobacterium woodii: proposal for residues involved in Na+ binding

AbstractNa+ transport through the F0 domain of Na+-F1F0-ATPases involves the combined action of subunits c and a but the residues involved in Na+ liganding in subunit a are unknown. As a first step towards the identification of these residues, we have cloned and sequenced the gene encoding subunit a of the Na+-F1F0-ATPase of Acetobacterium woodii. This is the second sequence available now for this subunit from Na+-F1F0-ATPases. A comparison of subunit a from Na+-F1F0-ATPases with those from H+-translocating enzymes unraveled structural similarity in a C-terminal segment including the ultimate and penultimate transmembrane helix. Seven residues are conserved in this region and, therefore, likely to be involved in Na+ liganding