The molecular structure of an axle-less F1-ATPase

Abstract

F1Fo ATP synthase is a molecular rotary motor that can generate ATP using a transmembrane proton motive force. Isolated F1-ATPase catalytic cores can hydrolyse ATP, passing through a series of conformational states involving rotation of the central {gamma} rotor subunit and the opening and closing of the catalytic {beta} subunits. Cooperativity in F1-ATPase has long thought to be conferred through the {gamma} subunit, with three key interaction sites between the {gamma} and {beta} subunits being identified. Single molecule studies have demonstrated that the F1 complexes lacking the {gamma} axle still "rotate" and hydrolyse ATP, but with less efficiency. We solved the cryogenic electron microscopy structure of an axle-less Bacillus sp. PS3 F1-ATPase. The unexpected binding-dwell conformation of the structure in combination with the observed lack of interactions between the axle-less {gamma} and the open {beta} subunit suggests that the complete {gamma} subunit is important for coordinating efficient ATP binding of F1-ATPase.