Topological and functional aspects of the proton conductor, F0, of the Escherichia coli ATP-synthase.

The isolated H+ conductor, F0, of the Escherichia coli ATP-synthase consists of three subunits, a, b, and c. H+-permeable liposomes can be reconstituted with F0 and lipids; addition of F1-ATPase reconstitutes a functional ATP-synthase. Mutants with altered or missing F0 subunits are defective in H+ conduction. Thus, all three subunits are necessary for the expression of H+ conduction. The subunits a and b contain binding sites for F1. Computer calculations, cross-links, membrane-permeating photo-reactive labels, and proteases were used to develop tentative structural models for the individual F0 subunits.