Cytochrome o (bo) is a proton pump in Paracoccus denitrificans and Escherichia coli

Abstract

Spheroplasts from aerobically grown wild-type Paracoccus denitrificans cells respire with succinate despite specific inhibition of the cytochrome bc ₁ complex by myxothiazol. Coupled to this activity, which involves only b-type cytochromes, there is translocation of 1.5–1.9 H⁺/e⁻ across the cytoplasmic membrane. Similar H⁺ translocation ratios are observed during oxidation of ubiquinol in spheroplasts from aerobically grown mutants of Paracoccus lacking cytochrome c oxidase, or deficient in cytochrome c, as well as in a strain of E. coli from which cytochrome d was deleted. These observations show that the cytochrome o complex is a proton pump much like cytochrome aa ₃ to which it is structurally related.