Structure and Mechanisms of F-Type ATP Synthases.

FF ATP synthases produce most of the ATP in the cell. F-type ATP synthases have been investigated for more than 50 years, but a full understanding of their molecular mechanisms has become possible only with the recent structures of complete, functionally competent complexes determined by electron cryo-microscopy (cryo-EM). High-resolution cryo-EM structures offer a wealth of unexpected new insights. The catalytic F head rotates with the central -subunit for the first part of each ATP-generating power stroke. Joint rotation is enabled by subunit acting as a flexible hinge between F and the peripheral stalk. Subunit conducts protons to and from the -ring rotor through two conserved aqueous channels. The channels are separated by ∼6 Å in the hydrophobic core of F, resulting in a strong local field that generates torque to drive rotary catalysis in F. The structure of the chloroplast FF complex explains how ATPase activity is turned off at night by a redox switch. Structures of mitochondrial ATP synthase dimers indicate how they shape the inner membrane cristae. The new cryo-EM structures complete our picture of the ATP synthases and reveal the unique mechanism by which they transform an electrochemical membrane potential into biologically useful chemical energy.