Spotlighting motors and controls of single FoF1-ATP synthase

Subunit rotation is the mechanochemical intermediate for the catalytic activity of the membrane enzyme FoF1-ATP synthase. smFRET (single-molecule FRET) studies have provided insights into the step sizes of the F-1 and F-o motors, internal transient elastic energy storage and controls of the motors. To develop and interpret smFRET experiments, atomic structural information is required. The recent F-1 structure of the Escherichia coli enzyme with the epsilon-subunit in an inhibitory conformation initiated a study for real-timemonitoring of the conformational changes of epsilon. The present mini-review summarizes smFRET rotation experiments and previews new smFRET data on the conformational changes of the CTD (C-terminal domain) of e in the E. coli enzyme.