Protonmotive force synthase

A crucially important finding is that submitochon-drial particles or vesicles from broken chloroplasts will synthesize ATP from ADP and P , when an artificial pH gradient is imposed.172186 Isolated purified FjF0 ATPase from a thermophilic Bacillus has been coreconstituted into liposomes with the light-driven proton pump bacteiiorhodopsin (Chapter 23). Illumination induced ATP synthesis.187 These observations support Mitchell s proposal that the ATP synthase is both spatially separate from the electron carriers in the membrane and utilizes the protonmotive force to make ATP. Thus, the passage of protons from the outside of the mitochondria back in through the ATP synthase induces the formation of ATP. What is the stoichiometry of this process ... 

It is currently believed that the translocation of 3 protons through the ATP synthase is required for each ATP molecule synthesized. (The transfer of an additional proton is required for the transport of ATP and OH- out of the matrix in exchange for ADP and P ) It now appears that the effect of protonmotive force is to induce a three-step rotation of 120° each of the F channel unit. The rotor (or revolving) component of this molecular machine consists of subunits e, y and c12, whereas subunits a, b2, 5, a3, and fi3 comprise the stator (or stationary) component. 

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