Electron and Proton Transport in Rhodospirillum rubrum Chromatophores

1. Cytochrome c2 in the soluble state transferred 1 electron (n=l) in the redox reaction at pH 5.5–9.8. Soluble and chromatophore-bound cytochrome cd transferred 2 electrons at pH 5.0–5.5 and 1 electron at pH 7.0–9.5. The proton transfer number, (n–a), was different for soluble and bound cytochrome cc' over the pH range tested. 2. For bound ubiquinone-10, n was 2 over the pH range tested; the ina) values were 2 at pH 5.5–8.0 and 1 at pH 8.0–9.0 3. The reduction of bound cytochrome cc' by succinate and the reduction of bound cytochrome B by NADH, were unchanged in D2O. However, the reduction of bound ubiquinone-10 by succinate and the reduction of added cytochrome c2 by NADH and by succinate were significantly inhibited. 4. The rates of ATP formation in the light, of ATP hydrolysis in the dark, and of ATP-Pi exchange in the dark, were inhibited to 41, 68, and 77%, respectively in 97% D2O.