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

F1Fo 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 \"rotor\" and peripheral \"stator\" stalk. Proton flow through the Fo motor generates rotation of the central stalk that induces conformation changes that catalyze production of ATP in the F1 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 F1Fo ATP synthase to provide a framework to interpret mutagenesis studies, we describe a rotational sub-step of the Fo motor c-ring associated with long-range conformational changes that suggests an elegant mechanism by which the F1 and Fo motors can be coupled with minimal energy loss.