Beef heart mitochondrial bc 1 complex (ubiquinone—cytochrome c oxidoreductase) has been assayed by its ability to catalyse the reaction of duroquinol reduction of ferricytochrome c. When the isolated complex is reincorporated into lipid vesicles, the enzyme-catalysed electron transfer rate becomes uncoupler-sensitive. Initial experiments suggest that a protonmotive force is generated across the vesicles when electron transfer is initiated. Both ΔΨ and ΔpH components of this protonmotive force then influence an internal rate constant of the bc 1 complex.
