Proton translocation by the mitochondrial cytochrome b-c1 complex is inhibited by NN'-dicyclohexylcarbodi-imide

NN'-Dicyclohexylcarbodi-imide at low concentrations decreases the H+/2e ratio for rat liver mitochondria over the span succinate to oxygen from 5.9 +/- 0.3 (mean +/- S.E.M.) to 4.0 +/- 0.1 and for the cytochrome b-c1 complex from 3.8 +/- 0.2 to 1.9 +/- 0.1, but has little effect on the H+/2e ratio of cytochrome oxidase. The decrease in stoicheiometry is due, not to uncoupling or inhibition of electron transport, but to inhibition of proton translocation. NN'-Dicyclohexylcarbodi-imide thus 'decouples' proton translocation in the cytochrome b-c1 complex.