Anatomy of F-1-ATPase powered rotation

作者：Martin James L; Ishmukhametov Robert; Hornung Tassilo; Ahmad Zulfiqar; Frasch Wayne D^*

来源：Proceedings of the National Academy of Sciences, 2014, 111(10): 3715-3720.

DOI：10.1073/pnas.1317784111

• FoF1
• torque
• rotary motor
• ATP hydrolysis

F-1-ATPase, the catalytic complex of the ATP synthase, is a molecular motor that can consume ATP to drive rotation of the.-subunit inside the ring of three alpha beta-subunit heterodimers in 120 degrees power strokes. To elucidate the mechanism of ATPase-powered rotation, we determined the angular velocity as a function of rotational position from single-molecule data collected at 200,000 frames per second with unprecedented signal-to-noise. Power stroke rotation is more complex than previously understood. This paper reports the unexpected discovery that a series of angular accelerations and decelerations occur during the power stroke. The decreases in angular velocity that occurred with the lower-affinity substrate ITP, which could not be explained by an increase in substrate-binding dwells, provides direct evidence that rotation depends on substrate binding affinity. The presence of elevated ADP concentrations not only increased dwells at 35 degrees from the catalytic dwell consistent with competitive product inhibition but also decreased the angular velocity from 85 degrees to 120 degrees, indicating that ADP can remain bound to the catalytic site where product release occurs for the duration of the power stroke. The angular velocity profile also supports a model in which rotation is powered by Van der Waals repulsive forces during the final 85 degrees of rotation, consistent with a transition from F-1 structures 2HLD1 and 1H8E (Protein Data Bank).

• 出版日期2014-3-11