Structure of a Cytochromeb-c1Complex fromSaccharomyces cerevisiaeYF

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Abstract
An isolation and purification procedure is reported for an active cytochrome b-c1 complex from S. cerevisiae. The complex acts as an antimycin A-sensitive duroquinone-cytochrome c reductase and contains cytochromes b and c1 at a concentration of 8 nmol/mg protein and non-heme Fe at a concentration of 15 nmol/mg protein. Difference spectra at room temperature and at 70.degree. K show that the preparation is free from contamination with cytochromes c or aa3. Assays of enzyme activity indicate the absence of any of the other catalytic functions normally associated with the mitochondrial respiratory chain. On dissociation and separation on sodium dodecylsulfate-polyacrylamide gels the complex gives rise to 7 bands correspondong to subunit polypeptide MW of 43,000, 40,000, 32,000, 24,000, 22,000, 20,000 and 18,000. These appear in a regular stoichiometry of 1:1:3:1:1:1:1.