Characterization of a new membrane-bound cytochrome c of Rhodopseudomonas capsulata

A cytochrome c (cyt. c) was solubilized with Triton-X-100 and co-purified with cytochrome c oxidase from membranes of chemotrophically grown cells of Rhodopseudomonas capsulata. Cyt. c and cytochrome oxidase were separated on Sephadex G-50 columns. Antibodies against cytochrome c2 from the same bacterium did not cross react with the membrane-bound cyt. c. The IEP of the membrane-bound cyt. c was found to be pH 8.2, the midpoint potential was 234 +/- 11 mV at pH 7.0. This cyt. c binds CO. The native cyt. c is a dimer with an apparent Mr of 25000 containing 2 mol heme per mol dimer, which is believed to function as an electron donor for the high-potential cytochrome c oxidase.