The six steps of the F1-ATPase rotary catalytic cycle

F 1 F o ATP synthase interchanges phosphate transfer energy and proton motive force via a rotary catalysis mechanism. When isolated, its F 1 -ATPase catalytic core can hydrolyze ATP, rotating its γ rotor subunit. Although previous structural studies have contributed greatly to understanding rotary catalysis in F 1 , the structure of one major conformational state detected in single-molecule studies, termed the binding dwell state, has not yet been determined. Here, by exploiting a temperature-sensitive F 1 -ATPase mutant from Bacillus PS3, the structure of this binding dwell state was established together with that of the catalytic dwell state. Each state showed three catalytic β subunits in different conformations, providing the complete set of six β subunit conformational states taken up during catalysis cycle. These structures provide molecular details for the power-stroke conformational change that occurs upon ATP binding and induces a ~80° γ subunit rotation, as well as a second torque-generating conformational change, triggered by hydrolysis and product release, that produces a ~40° rotation. This study also identifies a putative phosphate-releasing tunnel that indicates how ADP and phosphate releasing steps are coordinated. Overall these findings provide a structural basis for the entire F 1 -ATPase rotary catalysis cycle.