Hydrophobic Interactions of Cytochrome c Oxidase

Abstract

The binding of rat liver cytochrome c oxidase to phenyl‐Sepharose and various alkyl and ω‐aminoalkyl agarose gels has been studied. Deoxycholate‐solubilized cytochrome c oxidase was tightly bound to hexyl, octyl, ω‐aminohexyl, ω‐aminooctyl agarose as well as to phenyl‐Sepharose. This hydrophobic interaction was used for the purification of cytochrome c oxidase. The enzyme which was eluted from phenyl‐Sepharose was devoid of NADH (NADPH)‐acceptor reductase activities. The heme a content was 15.4 nmol per mg of protein. The purified enzyme was resolved into seven polypeptides upon polyacrylamide gel electrophoresis in sodium dodecylsulfate with molecular weights of 40000, 23200, 21500, 14500, 12600, 8900, and 4900. Antibodies raised in rabbits against the pure enzyme did not cross‐react with cytochrome c oxidases from either beef heart or yeast mitochondria. Cytochrome c oxidase bound to octyl‐Sepharose or phenyl‐Sepharose exhibited a very low catalytic activity. The possible modes of interaction of cytochrome c oxidase with the hydrophobic ligands are discussed.