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An alternative cytochrome oxidase of Paracoccus denitrificans functions as a proton pump



An alternative cytochrome oxidase of Paracoccus denitrificans functions as a proton pump



Biochimica Et Biophysica Acta. 1186(1-2): 100-106



Deletion of the genes encoding subunit I of cytochrome aa-3 in P. denitrificans yields mutants that lack cytochrome aa-3 but which are still capable of oxidizing ubiquinol by O-2 via the cytochrome bc-1 complex, as revealed by myxothiazol-sensitive respiration on succinate. An alternative terminal oxidase must be responsible for the myxothiazol-sensitive activity. The H+/e- ratio of proton translocation by mutant cells approached 3.0 for oxidation of succinate by O-2, while it was near 2.0 either with ferricyanide as electron acceptor (engaging the bc-1 complex only), or with O-2 as acceptor in the presence of myxothiazol (engaging the ubiquinol oxidase). However, proton translocation coupled to oxidation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) plus ascorbate amounted to much less than 1.0 H+/e-. This may be due to interference by another TMPD-oxidising activity that is not engaged during electron flux to oxygen via the cytochrome bc-1 complex. We conclude that Paracoccus can express an alternative cytochrome b-containing terminal oxidase, which translocates protons at least when operating in conjunction with the cytochrome bc-1 complex.

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Accession: 008139709

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DOI: 10.1016/0005-2728(94)90140-6



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