On the relationship between rate of ATP synthesis and H+ electrochemical gradient in rat-liver mitochondria.
The relationship between rate of ATP synthesis, JATP, and value of the proton electrochemical gradient, delta mu H, has been analyzed in intact mitochondria. Onset of phosphorylation causes a depression of delta mu H of 1.5 kJ/mol. There is a close parallelism between inhibition of JATP and restoration of delta mu H to its state-4 value during titrations with oligomycin or atractyloside. Titrations with ionophores display the following features: (a) delta mu H can be depressed by 3-4 kJ/mol by valinomycin + K+ without affecting the rate of ATP synthesis; (b) uncouplers abolish JATP completely while depressing delta mu H by 3 kJ/mol; (c) complete abolition of ATP synthesis by inhibitors of electron transport is accompanied by a depression of delta mu H of only 1 kJ/mol. The results indicate that: (a) there is a close functional relationship between redox and ATPase H+ pumps, whereby inhibition of electron transfer is accompanied by simultaneous inhibition of the ATPase H+ pumps; and (b) uncoupling of oxidative phosphorylation is not due to depression of delta mu H per se. The consistence of the present data with either a chemiosmotic model where delta mu H is the sole and obligatory intermediate for energy coupling, or models where there is a direct transfer of energy between the two pumps is discussed.
D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D004114:Dimethadione; D004563:Electrochemistry; D004735:Energy Transfer; D007700:Kinetics; D008930:Mitochondria, Liver / Q000378:metabolism*; D009861:Onium Compounds; D010084:Oxidation-Reduction; D011485:Protein Binding; D011522:Protons; D051381:Rats; D014320:Triphenylmethyl Compounds
D009861:Onium Compounds; D011522:Protons; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D000255:Adenosine Triphosphate; D004114:Dimethadione