36° step size of proton-driven c-ring rotation in F o F 1-ATP synthase

Abstract

Synthesis of adenosine triphosphate ATP, the biological energy currency, is accomplished by F o F 1-ATP synthase. In the plasma membrane of Escherichia coli, proton-driven rotation of a ring of 10 c subunits in the F o motor powers catalysis in the F 1 motor. Although F 1 uses 120° stepping during ATP synthesis, models of F o predict either an incremental rotation of c subunits in 36° steps or larger step sizes comprising several fast substeps. Using single-molecule fluorescence resonance energy transfer, we provide the first experimental determination of a 36° sequential stepping mode of the c-ring during ATP synthesis. © 2009 European Molecular Biology Organization.