SPECIES-SPECIFIC EXPRESSION OF CYTOCHROME-C-OXIDASE ISOZYMES

Cytochrome c oxidase was isolated from livers and hearts of sheep, dog and rabbit, and the polypeptide composition was analyzed by two diffe rent SDS-PAGE separation systems. The gels were blotted on PVDF-membra nes and the N-terminal amino acid sequences of the tissue-specific sub units VIa, VIIa and VIII were determined in a protein sequencer. Excep t for subunit VIIa from rat, subunits Via and VIIa from all investigat ed mammals are tissue-specific expressed in liver and heart, In contra st, subunit VIII is clearly different in liver and heart of bovine, do g and rat, but identical in liver and heart of human (liver-type), she ep, rabbit and also in rainbow trout (heart-type). The data suggest a strong species-specific variation of the regulatory properties of cyto chrome c oxidase in different tissues.