ATP synthases with novel rotor subunits:: New insights into structure, function and evolution of ATPases

ATPases with unusual membrane-embedded rotor subunits were found in both F1F0 and A(1)I(0) ATP synthases. The rotor subunit it c of A(1)A(0) ATPases is, in most cases. similar to subunit it C from F-0. Surprisingly, multiplied c subunits with four, six, or even 26 transmembrane spans have been found in some archaea and these multiplication events were sometimes accompanied by loss of the ion-translocating, group. Nevertheless, these enzymes are still active as ATP synthases. A duplicated c subunit with only one ion-translocating group Was found along with "normal" F-0 C subunits in the Na+ F1F0 ATP synthase of the bacterium Acetobacterium woodii. These extraordinary features and exceptional structural and functional variability in the rotor of ATP synthases may have arisen as an adaptation to different cellular needs and the extreme physicochemical conditions in the early history of life.