STUDIES ON OXIDATIVE PHOSPHORYLATION .17. PHYSICAL AND CHEMICAL PROPERTIES OF FACTOR B

Factor B, a protein component of the mitochondrial energy conservation system, has been purified by an improved procedure and some of its physical and chemical properties have been described. The purity of Factor B was evaluated by its appearance as a single component in disc gel electrophoresis, its sedimentation as a single component in a sucrose density gradient, and its sedimentation as a single peak in the analytical ultracentrifuge. Amino acid analysis of this protein has shown no unusual features. It has two tryptophans and four cysteic acids (by performic acid oxidation) per 29,200 g. Two of the sulfurs react with iodoacetamide. This protein has an unusually low affinity to the staining dyes, amido black and ponceau red. The presence of a functionally active thiol group (or groups) in Factor B was demonstrated by inactivation with p-chloromercuriphenylsulfonate, or iodine, and reactivation by dithiothreitol. © 1969.