Selective labeling of beef heart cytochrome oxidase subunit III with eosin-5-maleimide.
Cytochrome c oxidase has been isolated from beef heart mitochondria and labeled with the fluorochrome eosin-5-maleimide (EMA) after pretreatment with mersalyl. On SDS-polyacrylamide gels, EMA fluorescence and absorption occurred at a single band corresponding to subunit III. Since only Cys 115 of the two cysteinyl residues of subunit III had been shown to be reactive towards water-soluble SH-reagents, it was concluded that this residue was the one labeled by EMA. The EMA/enzyme ratio was about 1. Gel filtration experiments have shown that upon treatment with dicyclohexylcarbodiimide, subunit III was loosened from the complex; this result suggests that the inhibitory effect of dicyclohexylcarbodiimide on the H+-translocation activity may be related to such a phenomenon.
Müller
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M
Azzi
A
A
D000818:Animals; D002417:Cattle; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000032:analysis*; D004801:Eosine Yellowish-(YS) / Q000031:analogs & derivatives*; D009206:Myocardium / Q000201:enzymology*
D004024:Dicyclohexylcarbodiimide; C033531:eosin maleimide; D003576:Electron Transport Complex IV; D004801:Eosine Yellowish-(YS)