On the Molecular Weight of Mitochondrially Synthesized Subunits of Rat Liver Cytochrome Oxidase

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Abstract
The subunit composition of cytochrome c oxidase from rat liver mitochondria was studied by dodecylsulfate polyacrylamide gel electrophoresis. The apparent MW of the 7 subunits were in reasonable agreement with published data on cytochrome c oxidase subunits from other sources. Two additional subunits were found if the electrophoresis was performed with 8 M urea, due to splitting of the smallest subunit. Performic acid oxidation of the isolated subunits I and II increased the apparent MW from 38,000-48,000 and from 24,500-29,000, respectively, accompanied by a normalization of the anomalous behaviour of subunit I in the Ferguson plot. It was suggested that performic acid, by splitting extremely inaccessible disulfide bridges, mediated full complexing of the subunits by dodecylsulfate, thus permitting the determination of the real MW by dodecylsulfate polyacrylamide gel electrophoresis.