Structure and function of the A1A0-ATPases from methanogenic Archaea.

Recent molecular studies revealed nine to ten gene products involved in function/assembly of the methanoarchaeal ATPase and unravel a close relationship of the A1A0-ATPase and the V1V0-ATPase with respect to subunit composition and the structure of individual subunits. Most interestingly, there is an astonishing variability in the size of the proteolipids in methanoarchaeal A1A0-ATPases with six, four, or two transmembrane helices and a variable number of conserved protonizable groups per monomer. Despite the structural similarities the A1A0-ATPase differs fundamentally from the V1V0-ATPase by its ability to synthesize ATP, a feature shared with F1F0-ATPases. The discovery of duplicated and triplicated versions of the proteolipid in A1A0-ATP synthases questions older views of the structural requirements for ATP synthases versus ATP hydrolases and sheds new light on the evolution of these secondary energy converters.