Purification and characterization of low potential c cytochromes from Desulfovibrio desulfuricans membranes

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Abstract
Desulfovibrio desulfuricans grown in a lactate‐sulfate medium produces, in addition to soluble cytochromes, c‐type cytochromes which appear to be integral membrane proteins. Two cytochromes can be separated, an abundant 15 kDa cytochrome and a 22 kDa cytochrome. Both have optical spectra characteristics of c‐type cytochromes. The 15 kDa cytochrome shows two n = 1 components in potentiometric redox titrations with midpoint potentials at −130 and −270 mV in the membrane; both were slightly lower in detergent‐solubilized preparations. We suggest a designation of cytochrome cc m for this species. Its properties suggest a function as a transmembrane electron carrier between hydrogen and sulfate.