Cytochrome c oxidase from baker's yeast contains three mitochondrially made subunits (I to III) which are relatively hydrophobic and four cytoplasmically made subunits (IV to VII) which are relatively hydrophilic (Mason, T. L., Poyton, R. O., Wharton, D.C., and Schatz, G. (1973) J. Biol. Chem. 248, 1346-1354 and Poyton, R. O., and Schatz, G. (1975) J. Biol. Chem. 250, 752-761). In order to explore the arrangement of these subunits in the holoenzyme, the reactivity of each subunit with a variety of "surface probes" was tested with isolated cytochrome c oxidase, with cytochrome c oxidase incorporated into liposomes, and with mitochondrially bound cytochrome c oxidase. The surface probes included iodination with lactoperoxidase and coupling with p-diazonium benzenesulfonate. In addition, external subunits were identified by linking them to bovine serum albumin carrying a covalently bound isocyanate group. In the membrane-bound enzyme, Subunit I was almost completely inaccessible and Subunit II was partly inaccessible to all surface probes. All of the other subunits were accessible. Similar results were obtained with the solubilized enzyme, except that the differences in reactivity between the individual subunits were less clear-cut. The results obtained with liposome-bound cytochrome c oxidase resembled those obtained with the mitochondrially bound enzyme. These data suggest that the two largest mitochondrially made subunits are localized in the interior of the enzyme and that they are genuine components of cytochrome c oxidase.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|