Isolation, Purification, and Some Properties of Mammalian Cytochrome b

Abstract

There have been a number of reports in the literature on attempts to isolate and purify cytochrome b (l-6).All these preparations, however, contained other cytochrome contaminants, notably cytochrome cl and/or succinic dehydrogenase and cytochrome oxidase.Most recently in 1960 Bornstein et al. ( 7) reported the isolation of cytochrome b from beef heart mitochondria and estimated the molecular weight to be approximately 30,909.A rather wide range has been reported for the oxidation-reduction potential of cytochrome b.Ball (8) reported a value of -40 mv, whereas Hill in 1954 (9) stated that the value for the E'o for mammaliin cytochrome b should be closer to 0 mv.Chance (10) supported Hill's statement, whereas Okunuki and Sekuru (5) claimed a value of -50 mv for their preparation.Most recently, Colpa-Boonstra and Holton (11) reported a value of +77 mv.In a preliminary communication ( 12) we outlined a method for the isolation of mammalian cytochrome b that showed no spectral evidence of cytochrome cl contamination and was free of succinic dehydrogenase and cytochrome oxidase activity.The purpose of this communication is to describe in detail the steps in the isolation and purification of this preparation and to present some of its properties.The oxidation-reduction potential was found to be approximately +68 mv.