  Synthesis of the biological "energy currency molecule" adenosine triphosphate
ATP is accomplished by FoF1-ATP synthase. In the plasma membrane of Escherichia
coli, proton-driven rotation of a ring of 10 c subunits in the Fo motor powers
catalysis in the F1 motor. While F1 uses 120 degree stepping, Fo models predict
a step-by-step rotation of c subunits 36 degree at a time, which is here
demonstrated by single-molecule fluorescence resonance energy transfer.
