ATP synthases: structure, function and evolution of unique energy converters.

A-, F- and V-adenosine 5'-triphosphatases (ATPases) consist of a mosaic of globular structural units which serve as functional units. These ion-translocating ATPases are thought to use a common mechanism to couple energy of ATP hydrolysis to ion transport and thus create an electrochemical ion gradient across the membrane. In vitro, all of these large protein complexes are able to use an ion gradient and the associated membrane potential to synthesize ATP. A-/F-/V-type ATPases are composed of two distinct segments: a catalytic sector, A1/F1/V1, whose three-dimensional structural relationship will be reviewed, and the membrane-embedded sector, Ao/Fo/Vo, which functions in ion conduction. Recent studies on the molecular biology of the Ao/Fo/Vo domains revealed surprising findings about duplicated and triplicated versions of the proteolipid subunit and shed new light on the evolution of these ion pumps.