We have measured the rates of superoxide anion generation by cytochrome bc(1) complexes isolated from bovine heart and yeast mitochondria and by cytochrome bc(1) complexes from yeast mutants in which the midpoint potentials of the cytochrome b hemes and the Rieske iron-sulfur cluster were altered by mutations in those proteins. With all of the bc(1) complexes the rate of superoxide anion produc...

The 02, CO, and alkyl isocyanide-binding properties of a variety of vertebrate and invertebrate heme proteins have been compared in detail to those of protoheme mOn0-3-( 1-imidazoy1)-propylamide monomethyl ester in aqueous suspensions of soap micelles. The proteins examined include: cytochrome P-450,,, from Pseudomonasputida, beef heart cytochrome c oxidase, yeast cytochrome c peroxidase, a and...

This communication reports the generation of an electrostatic probe using chemical modification of methionine side chains. The alkylation of methionine by iodoacetamide was achieved in a set of Saccharomyces cerevisiae iso-1-cytochrome c mutants, introducing the nontitratable, nondelocalized positive charge of a carboxyamidomethylmethionine sulfonium (CAMMS) ion at five surface and one buried s...

We have examined the pre-steady state reduction kinetics of the Saccharomyces cerevisiae cytochrome bc(1) complex by menaquinol in the presence and absence of endogenous ubiquinone to elucidate the mechanism of triphasic cytochrome b reduction. With cytochrome bc(1) complex from wild type yeast, cytochrome b reduction was triphasic, consisting of a rapid partial reduction phase, an apparent par...