Abstract
Cytochrome bd is a terminal quinol oxidase in Escherichia coli. Mitochondrial respiration is inhibited at cytochrome bc(1) (complex III) by myxothiazol. Mixing purified cytochrome bd oxidase with myxothiazol-inhibited bovine heart submitochondrial particles (SMP) restores up to 50% of the original rotenone-sensitive NADH oxidase and succinate oxidase activities in the absence of exogenous ubiquinone analogs. Complex III bypassed respiration and is saturated at amounts of added cytochrome bd similar to that of other natural respiratory components in SMP. The cytochrome bd tightly binds to the mitochondrial membrane and operates as an intrinsic component of the chimeric respiratory chain.