Visualizing movements in E. coli F1Fo ATP synthase indicates how the F1 and Fo motors are coupled

F 1 F o ATP synthase functions as a biological rotary generator and makes a major contribution to cellular energy production. It is comprised of two motors that are coupled together by a central 9rotor9 and peripheral 9stator9 stalk. Proton flow through the F o motor generates rotation of the central stalk that induces conformation changes that catalyze production of ATP in the F 1 motor. Here we provide 3-4 A resolution cryo-EM structures of E. coli F1Fo ATP synthase in 10 mM MgADP. In addition to generating a comprehensive structural model of E. coli F 1 F o ATP synthase to provide a framework to interpret mutagenesis studies, we describe a rotational sub-step of the F o motor c-ring associated with long-range conformational changes that suggests an elegant mechanism by which the F 1 and F o motors can be coupled with minimal energy loss.