Electron microscopy of the F1F0 ATP synthase: from structure to function.

The F1F0 ATP synthase is the large multisubunit complex which uses the proton gradient of energetically active membranes to synthesize ATP. While biochemical and genetic approaches have characterized the composition of the enzyme and elucidated many details of its mechanism and assembly, electron microscopy has been the tool of primary importance in determining the arrangement of the many subunits which comprise the F1F0. The highly cooperative catalytic mechanism is tightly coupled to transmembrane proton translocation in a separate and rather distant sector of the complex. An understanding of this intricate process and its control requires an appreciation of subunit interactions, starting with their locations relative to one another. Electron microscopy has provided most of the available structural information on the F1F0, and recent applications of cryo-electron microscopy have captured different functionally relevant configurations which may finally address longstanding questions about subunit rearrangements during the catalytic cycle.