title: Energetics of ATP-driven reverse electron transfer from cytochrome c to fumarate and from succinate to NAD in submitochondrial particles.
abstract: The maximum Gibbs free energies of reverse electron transfer from succinate to NAD+ and from cytochrome c to fumarate driven by ATP hydrolysis in submitochondrial particles from beef heart were measured as a function of the Gibbs free energy of ATP hydrolysis. The ratio of the energies delta G'redox/delta G'ATP was 1.40 from succinate to NAD+ and 0.89 from cytochrome c to succinate. The ratio, equivalent to a thermodynamic P/2e-ratio, was dependent on whether the electrochemical proton gradient was primarily a membrane potential or a pH gradient for the cytochrome c to fumarate reaction. The results are consistent with H+/ATP = 3 for F1 ATPase, H+/2e- = 4 for NADH-CoQ reductase, and H+(matrix)/2e- = 2 for succinate-cytochrome c reductase.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D005650:Fumarates / Q000378:metabolism*; D008433:Mathematics; D008928:Mitochondria / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000648:ultrastructure; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D013367:Submitochondrial Particles / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism*; D019802:Succinic Acid
chemical_list: D003574:Cytochrome c Group; D005650:Fumarates; D013386:Succinates; D009243:NAD; C032005:fumaric acid; D000255:Adenosine Triphosphate; D019802:Succinic Acid