Role of subunit removal in modulating the acid-dependent 430-414 nm conversion in cytochrome c oxidase
Sumera, Nifta A.
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Acid-resistant and -sensitive conformers of cytochrome c oxidase are observed by varying the amount of dodecyl maltoside in the enzyme solution. Acid-resistance was evident only when the enzyme solution contained a low concentration of dodecyl maltoside (400 mol / mol heme A). Increasing the amount of the detergent by 20-fold converted the resistant to the sensitive conformer. Similar conditions have been reported to promote dissociation of subunits HI, Via, VIb and Vila. SDS-PAGE analysis, however, indicated that the conversion from the resistant to the sensitive conformer did not require the dissociation of these subunits. The acid-sensitive conformer was observed in the presence and absence of subunits III, Via, VIb and Vila. Additionally, the resistant conformer was observed under conditions where these subunits were removed. The possibility that the induction of the sensitive conformer is a direct effect on the catalytic core complex will be discussed.