Correlation between the numbers of rotation steps in the ATPase and proton-conducting domains of F- and V-ATPases

Abstract

This letter reports the correlation in the number of distinct rotation steps between the F1/V1 and Fo/Vo domains that constitute common rotary F- and V-ATP synthases/ATPases. Recent single-molecule studies on the F1-ATPase revealed differences in the number of discrete steps in rotary catalysis between different organisms—6 steps per turn in bacterial types and mitochondrial F1 from yeast, and 9 steps in the mammalian mitochondrial F1 domains. The number of rotational steps that Fo domain makes is thought to correspond to that of proteolipid subunits within the rotating c-ring present in Fo. Structural studies on Fo and in the whole ATP synthase complex have shown a large diversity in the number of proteolipid subunits. Interestingly, 6 steps in F1 are always paired with 10 steps in Fo, whereas 9 steps in F1 are paired with 8 steps in Fo. The correlation in the number of steps has also been revealed for two types of V-ATPases: one having 6 steps in V1 paired with 10 steps in Vo, and the other one having 3 steps in V1 paired with 12 steps in Vo. Although the abovementioned correlations await further confirmation, the results suggest a clear trend; ATPase motors with more steps have proton-conducting motors with less steps. In addition, ATPases with 6 steps are always paired with proton-conducting domains with 10 steps.