Effect of b-itc1-site inhibitors on the midpoint potentials of mitochondrial cytochromes b

AbstractAnaerobic potentiometric titrations of b cytochromes have been carried out in beef heart submitochondrial particles in the presence of several specific inhibitors of electron transfer through the b-c1-site of the respiratory chain. Whereas antimycin shows no significant effect on the titration curve of cytochrome b-562, NoHOQnO is found to shift the Em of b-562 by 20–30 mV to the positive. Funiculosin raises the Em of b-562 by > 100 mV and also appears to bring about a minor shift of b-566 midpoint potential. In the presence of myxothiazol, both b cytochromes with Em values 15–30 mV more positive than in the control