Cytochrome b₅₆₁ catalyzes transmembrane electron transfer

Purified cytochrome b₅₆₁ from bovine adrenal medulla chromaffin vesicles has been reconstituted into phosphatidylcholine vesicles by a detergent-dialysis method. When the reconstituted cytochrome-containing vesicles were preloaded with ascorbic acid and cytochrome c was added to the external medium, the internal ascorbic acid was able to reduce the external cytochrome c. This reduction of cytochrome c was dependent on the presence of cytochrome b₅₆₁ in the membrane and was not due to leakage of ascorbate from the vesicles. These results demonstrate that cytochrome b₅₆₁ catalyzes a transmembrane electron transfer.