Cryo-EM structures of the autoinhibited ATP synthase in three rotational states.

A molecular model that provides a framework for interpreting the wealth of functional information obtained on the F-ATP synthase has been generated using cryo-electron microscopy. Three different states that relate to rotation of the enzyme were observed, with the central stalk's ε subunit in an extended autoinhibitory conformation in all three states. The F motor comprises of seven transmembrane helices and a decameric c-ring and invaginations on either side of the membrane indicate the entry and exit channels for protons. The proton translocating subunit contains near parallel helices inclined by ~30° to the membrane, a feature now synonymous with rotary ATPases. For the first time in this rotary ATPase subtype, the peripheral stalk is resolved over its entire length of the complex, revealing the F attachment points and a coiled-coil that bifurcates toward the membrane with its helices separating to embrace subunit from two sides.