Purification and some properties of soluble cytochromes, cytochrome c-551 and cytochrome c-550, from a facultative methylotroph, protaminobacter ruber strain NR-1

Two soluble cytochromes of the C-type, cytochrome c-551 and cytochrome c-550, were purified from the bacteriochlorophyll-containing cells of a facultative methylotroph, Protaminobacter ruber Strain NR-1, by ion-exchange chromatography and gel-filtration.Cytochrome c-551 had absorption maxima at 551, 522 and 416 nm in the reduced form, and at 525, 410 and 273 nm in the oxidized form. This cytochrome was a slightly basic protein with an isoelectric point of 8.4. It had a mid-point redox potential of 272 mV at pH 7.0. The molecular weight of this protein was 13,500 and 13,700 by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel-filtration, respectively.Cytochrome c-550 had absorption maxima at 550, 522 and 415 nm in the reduced form, and at 527, 409 and 278 nm in the oxidized form. This cytochrome was acidic, having an isoelectric point of 4.3. It had a mid-point redox potential of 227 mV at pH 7.0. Its molecular weight was 19,500 and 22,000 by SDS-PAGE and gel-filtration, respectively.