The motor of the ATP synthase.

A model is presented in which ion translocation through the F-0 part of the ATP synthase drives the rotation of the ring of c subunits (rotor) versus the a subunit (stator). The coupling ion binding sites on the rotor are accessible from the cytoplasm of a bacterial cell except for the c subunit at the interface to the stator. Here, the binding site is accessible from the periplasm through a channel formed by subunit a. In the ATP synthesis mode, a coupling ion is anticipated to pass through the stator channel into the binding site of the adjacent rotor subunit, following the electrical potential. Occupation of this site triggers, probably by electrostatic forces, the rotation of the ring. This makes the binding site accessible to the cytoplasm, where the coupling ion dissociates. Simultaneously, this rotation moves again an empty rotor subunit into the contact site with the stator, where its binding site becomes loaded and rotation continues. (C) 1998 Elsevier Science BN.