Preparation and Properties of Cardiac Cytochrome c1

Abstract In a continuation of our studies of the sequential fragmentation of the respiratory chain, we have worked out a method of isolating cytochrome c1 from succinate cytochrome c reductase. The purified cytochrome c1 was stable in neutral solution and soluble in aqueous media. It contained 25 nmoles of heme per mg of protein and a small amount of carbohydrate. The absorption spectrum of the reduced cytochrome c1 possessed maxima at 552.5, 530, 522.5, 512, 417, 317, and 276 nm, and the oxidized at 558, 522, 411, 355, and 276 nm. Neither carbon monoxide nor oxygen affected its spectral behavior. At -160°, the α-band of reduced cytochrome c1 split into at least three bands and the β-band into nine. The low temperatures intensified the α- and β-bands by 6- to 7-fold but did not cause any significant shift of the positions of the maxima. The extinction coefficient at 23° for Ared552.5 — Ared540 was found to be 17.5 mm-1 cm-1 from the total iron assay and 18.5 by titration with DPNH in the presence of phenazine methosulfate. The cytochrome c1 can be used as an electron donor or acceptor in interaction with the electron transfer system in submitochondrial particles of bovine heart.