Structure and function of the A(1)A(0)-ATPases from methanogenic archaea

Recent molecular studies revealed nine to ten gene products involved in fun ction/assembly of the methanoarchaeal ATPase and unravel a close relationsh ip of the A(1)A(0)-ATPase and the V1V0-ATPase with respect to subunit compo sition and the structure of individual subunits. Most interestingly, there is an astonishing variability in the size of the proteolipids in methanoarc haeal A(1)A(0)-ATPases with six, four, or two transmembrane helices and a v ariable number of conserved protonizable groups per monomer. Despite the st ructural similarities the A(1)A(0)-ATPase differs fundamentally from the V1 V0-ATPase by its ability to synthesize ATP, a feature shared with F1F0-ATPa ses. The discovery of duplicated and triplicated versions of the proteolipi d in A(1)A(0)-ATP synthases questions older views of the structural require ments for ATP synthases versus ATP hydrolases and sheds new light on the ev olution of these secondary energy converters.