Mechanism of ATP hydrolysis dependent rotation of bacterial ATP synthase

Abstract

F₁ domain of ATP synthase is a rotary ATPase complex in which rotation of central γ-subunit proceeds in 120° steps against a surrounding α₃β₃ fueled by ATP hydrolysis. How the ATP hydrolysis reactions occurring in three catalytic αβ dimers are coupled to mechanical rotation is a key outstanding question. Here we describe catalytic intermediates of the F₁ domain in F_oF₁ synthase from Bacillus PS3 sp. during ATP mediated rotation captured using cryo-EM. The structures reveal that three catalytic events and the first 80° rotation occur simultaneously in F₁ domain when nucleotides are bound at all the three catalytic αβ dimers. The remaining 40° rotation of the complete 120° step is driven by completion of ATP hydrolysis at α_Dβ_D, and proceeds through three sub-steps (83°, 91°, 101°, and 120°) with three associated conformational intermediates. All sub-steps except for one between 91° and 101° associated with phosphate release, occur independently of the chemical cycle, suggesting that the 40° rotation is largely driven by release of intramolecular strain accumulated by the 80° rotation. Together with our previous results, these findings provide the molecular basis of ATP driven rotation of ATP synthases.

The ATP synthase F_oF₁ undergoes rotation in discrete 120° steps. Using cryo-EM analysis, the authors characterise intermediate structures within these 120° steps at 81°, 83°, 91°, and 101°. This shows that F_oF₁ undergoes a total of 15 steps in a 360° rotation, exhibiting multiple discreet movements per full rotation as opposed to one fluid motion.