Conformational coupling in H+-pumps and ATP synthesis--its analysis with anisotropic inhibitors of energy transduction in oxidative phosphorylation.

The analysis of anisotropic inhibitor-induced phenomena in mitochondria revealed that two kinds of negative charges are generated near surface of the C-side of mitochondrial inner membranes in the energized state, on the redox complexes (I, III & IV) and F0, respectively, and that positively charged anisotropic inhibitors (AI+) inhibit energy transduction in oxidative phosphorylation by binding to these negative charges. Thus, AI+ have two different inhibition sites in oxidative phosphorylation, the redox complexes and F0. The membrane components generating the negative charges in energized mitochondria were examined by the technique of photoaffinity labeling with monoazide ethidium, which is an AI+. Results showed that monoazide ethidium specifically binds to two kinds of hydrophobic protein (of 8 K and 13 K daltons) of mitochondria energized with succinate, and these proteins were named chargerin I and II, respectively. Chargerin I and II, which may be components of the redox complexes and Fo, seem to generate the negative charges described above, and these may be essential for H+-pumps in the redox complexes and F1 X F0. AI+ seem to inhibit ATP synthesis by binding to negatively charged sites of chargerin I and II. Based on these findings and the salient results on energy-transducing membranes obtained recently in other laboratories, a conformational model of H+-pumps and ATP synthesis in mitochondria is proposed, which is also applicable to ATP synthesis in other energy-transducing membranes and ATP-linked active transport of ions.