Isolation, Purification and Some Properties of Cytochrome c-551 from Chromatium vinosum

Abstract

Cytochrome c-551 was isolated and purified from a photosynthetic bacterium Chromatium vinosum by ammonium sulfate fractionation, ion-exchange chromatography and gel filtration. The cytochrome had absorption maxima at 280, 407 and 523–524 nm in the oxidized form, and 416, 521 and 549.5 nm in the reduced form. The reduced-minusoxidized difference millimolar absorption coefficient was 9.90 mM−1cm−1 for the wavelength pair, 550.5 minus 540 nm. The molecular weight of the cytochrome was 16,000 by gel filtration on Sephadex G-100 and 15,500 by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The midpoint redox potential was +240 mV at pH 8.0. Cytochrome c-551 was released from bacterial cells when spheroplasts were produced but EDTA and lysozyme treatments. The released cytochrome had the same properties as those of the cytochrome preparation obtained by disruption of cells through a French pressure cell. This confirms the earlier suggestion that cytochrome c-551 is located in the periplasmic space of cells.