Fo-driven Rotation in the ATP synthase Direction Against the Force of F1ATPase in the FoF1 ATP synthase [Molecular Biophysics]

February 24th, 2015 by Martin, J., Hudson, J., Hornung, T., Frasch, W. D.

Living organisms rely on the FoF1 ATP synthase to maintain the non-equilibrium chemical gradient of ATP to ADP and phosphate that provides the primary energy source for cellular processes. How the Fo motor uses a transmembrane electrochemical ion gradient to create clockwise (CW) torque that overcomes F1ATPase-driven counterclockwise (CCW) torque at high ATP is a major unresolved question. Using single FoF1 molecules embedded in lipid bilayer nanodiscs, we now report the observation of Fo-dependent rotation of the c10-ring in the ATP synthase (CW) direction against the CCW force of ATPase-driven rotation that occurs upon formation of a leash with Fo-stator subunit-a. Mutational studies indicate that the leash is important for ATP synthase activity, and support a mechanism in which residues aE196 and cR50 participate in the cytoplasmic proton half-channel to promote leash formation.