title: Energy conservation and uncoupling in mitochondria.
abstract: Energy conservation and uncoupling in mitochondria are examined in the light of three important new findings: (a) Studies with the photoaffinity-labeling uncoupler 2-azido-4-nitrophenol have shown that mitochondria contain a specific uncoupler binding site (apparently a polypeptide of Mr = 30,000 +/- 10%). (b) This site fractionates into an enzyme complex (complex V), which is capable of oligomycin- and uncoupler-sensitive ATP-Pi exchange. It is absent from electron transfer complexes I, III, and IV, which represent segments of the respiratory chain containing coupling sites 1, 2, and 3, respectively. (c) Trinitrophenol is a membrane-impermeable uncoupler (uncouples submitochondrial particles, but not mitochondria) and a poor protonophore. There is an excellent correlation between the uncoupling potencies and the affinities of uncouplers for the mitochondrial uncoupler-binding site. There is no correlation between uncoupling potency and protonophoric activity of uncouplers when a membrane-permeable uncoupler is compared with a membrane-impermeable one.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D003486:Cyanides / Q000494:pharmacology; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004140:Dinitrophenols / Q000378:metabolism* / Q000494:pharmacology; D008564:Membrane Potentials; D008566:Membranes / Q000378:metabolism; D008928:Mitochondria / Q000648:ultrastructure; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism* / Q000494:pharmacology; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D014001:Tin / Q000494:pharmacology; D014475:Uncoupling Agents / Q000378:metabolism
chemical_list: D003486:Cyanides; D004140:Dinitrophenols; D009596:Nitrophenols; D014475:Uncoupling Agents; D004024:Dicyclohexylcarbodiimide; D014001:Tin; D000255:Adenosine Triphosphate; D011188:Potassium