Purification and Some Properties of Cytochrome c Oxidase from the Yeast Saccharomyces cerevisiae

A method is described for the purification of cytochrome c oxidase (EC 1.9.3.1) from a particulate fraction of Red Star yeast. The enzyme as isolated contains up to 7.2 nmoles of heme a per mg of protein and is free from contamination by hemes other than heme a. The spectrum of the reduced enzyme equilibrated with carbon monoxide is apparently dependent on the aggregation state of the enzyme. The fact that the enzyme is capable of assuming both a monomeric and a dimeric state of aggregation is demonstrated by sucrose density gradient centrifugation and susceptibility to dithionite reduction. After dissociation at 100° in sodium dodecyl sulfate-urea-mercaptoethanol, the enzyme shows four major polypeptide components when subjected to electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate and 6 m urea.