Iron-containing proteins in Chromatium I. Solubilization of membrane-bound cytochrome

Variations in the nature of the iron-containing proteins in Chromatium sp. strain D, grown under varying conditions of substrate and as a function of growth phase, are investigated. The results obtained show no significant changes induced by manipulation of these parameters. At least 80% of the heme protein present is membrane-bound and can be released only by detergent treatment. All but a small fraction is of c type, a minor protoheme component (cytochrome b′) being present. The membrane-bound cytochrome cannot be identified with those which are freely soluble.