Spectral Characterization of the Photoreducible b-Type Cytochrome of Dictyostelium discoideum

Irradiation of a soluble extract from broken cells of Dictyostelium discoideum causes the photoreduction of a b-type cytochrome. The cytochrome b can be separated from cytochrome c, which is also present in the extract, by column chromatography on Brushite, but the cytochrome b is no longer sensitive to light after separation on the column. Low temperature spectroscopy shows that reduced form of the photoreducible cytochrome b has a Soret band at 423 nm and a split α band with maxima at 558 and 551 nm similar to the b-type cytochrome in complex II of beef heart mitochondria.