High-Speed Atomic Force Microscopy Reveals Rotary Catalysis of Rotorless F1-ATPase

F-1 is an adenosine triphosphate (ATP)-driven motor in which three torque-generating beta subunits in the alpha(3)beta(3) stator ring sequentially undergo conformational changes upon ATP hydrolysis to rotate the central shaft gamma unidirectionally. Although extensive experimental and theoretical work has been done, the structural basis of cooperative torque generation to realize the unidirectional rotation remains elusive. We used high-speed atomic force microscopy to show that the rotorless F-1 still rotates; in the isolated alpha(3)beta(3) stator ring, the three beta subunits cyclically propagate conformational states in the counterclockwise direction, similar to the rotary shaft rotation in F-1. The structural basis of unidirectionality is programmed in the stator ring. These findings have implications for cooperative interplay between subunits in other hexameric ATPases.