Oxygen dependent electron transfer in the cytochrome bc1 complex

The effect of molecular oxygen on the electron transfer activity of the cytochrome bc₁ complex was investigated by determining the activity of the complex under the aerobic and anaerobic conditions. Molecular oxygen increases the activity of Rhodobacter sphaeroides bc₁ complex up to 82%, depending on the intactness of the complex. Since oxygen enhances the reduction rate of heme b_L, but shows no effect on the reduction rate of heme b_H, the effect of oxygen in the electron transfer sequence of the cytochrome bc₁ complex is at the step of heme b_L reduction during bifurcated oxidation of ubiquinol.