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Isolation of ubiquinol oxidase from Paracoccus denitrificans and resolution into cytochrome bc1 and cytochrome c-aa3 complexes.

1985; Elsevier BV; Volume: 260; Issue: 4 Linguagem: Inglês

10.1016/s0021-9258(18)89576-x

1083-351X

Edward A. Berry, Bernard L. Trumpower,

Coenzyme Q10 studies and effects

An enzyme complex with ubiquinol-cytochrome c oxidoreductase, cytochrome c oxidase, and ubiquinol oxidase activities was purified from a detergent extract of the plasma membrane of aerobically grown Paracoccus denitrificans.This ubiquinol oxidase consists of seven polypeptides and contains two b cytochromes, cytochrome cl, cytochrome aa3, and a previously unreported C-type cytochrome.This C-type cytochrome has an apparent M , of 22,000 and an (x absorption maximum at 552 nm.Retention of this c cytochrome through purification presumably accounts for the independence of ubiquinol oxidase activity on added cytochrome c.Ubiquinol oxidase can be separated into a 3-subunit bel complex, a 3-subunit c-au3 complex, and a 57-kDa polypeptide.This, together with detection of covalently bound heme and published molecular weights of cytochrome c1 and the subunits of cytochrome c oxidase, allows tentative identification of most of the subunits of ubiquinol oxidase with the prosthetic groups present.Ubiquinol oxidase contains cytochromes corresponding to those of the mitochondrial bel complex, cytochrome c oxidase complex, and a bound cytochrome c.Ubiquinol-cytochrome c oxidoreductase activity of the complex is inhibited by inhibitors of the mitochondrial b c l complex.Thus it seems likely that the pathway of electron transfer through the be, complex of ubiquinol oxidase is similar to that through the mitochondrial b e l complex.The number of polypeptides present is less than half the number in the corresponding mitochondrial complexes.This structural simplicity may make ubiquinol oxidase from P .denitrificans a useful system with which to study the mechanisms of electron transfer and energy transduction in the b e l and cytochrome c oxidase sections of the respiratory chain.The Gram-negative soil bacterium Paracoccus denitrificans has a respiratory chain which closely resembles that of mitochondria (1, 2).Cytochrome c oxidase has been isolated from P. denitrificans and shown to be similar to that of mitochondria in function and in prosthetic groups (3), but to consist of only two polypeptides as compared to at least seven polypep-