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 β subunits in the α(3)β(3) stator ring sequentially undergo conformational changes upon ATP hydrolysis to rotate the central shaft γ 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 α(3)β(3) stator ring, the three β 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.