Effect of the mitochondrial membrane potential on the absorbance of the reduced form of cytochrome c oxidase.

Autor: Covian R; Laboratory of Cardiac Energetics and Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, United States of America., Edwards LO; Laboratory of Cardiac Energetics and Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, United States of America., Balaban RS; Laboratory of Cardiac Energetics and Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, United States of America.
Jazyk: angličtina
Zdroj: Biochimica et biophysica acta. Bioenergetics [Biochim Biophys Acta Bioenerg] 2024 Aug 01; Vol. 1865 (3), pp. 149048. Date of Electronic Publication: 2024 May 07.
DOI: 10.1016/j.bbabio.2024.149048
Abstrakt: The effect of mitochondrial membrane potential (ΔΨ m ) on the absorbance of the reduced cytochrome c oxidase (COX) was evaluated in isolated rabbit heart mitochondria using integrating sphere optical spectroscopy. Maximal reduction of the mitochondrial cytochromes was achieved by either blowing nitrogen to remove oxygen, or by adding cyanide. Gradual depolarization of ΔΨ m by adding increasing concentrations of uncoupler resulted in an increase of up to 50 % in the absorbance of cytochrome aa 3 under nitrogen saturation, and of 25 % with cyanide. Cytochrome aa 3 absorbance increases were also observed in the presence of cyanide with apyrase (20 %) or oligomycin (12 %). The b L heme absorbance also decreased as expected from ΔΨ m depolarization. A ~ 1 nm red shift in the peak wavelength of cytochrome aa 3 was observed under anoxic conditions as ΔΨ m was depolarized. Importantly, cytochrome c and c 1 absorbances remained constant at levels corresponding to full reduction under all experimental manipulations of ΔΨ m , especially with cyanide. These data suggest that ΔΨ m -dependent changes in the absorbance of reduced COX were due to a variable extinction coefficient of heme a and/or a 3 as a function of ΔΨ m . A similar increase in the reduced cytochrome aa 3 absorbance without changes in cytochrome c and c 1 was observed in the perfused rabbit heart when decreasing ΔΨ m with uncoupler. Our results imply that COX absorbance in its fully reduced state does not simply reflect the oxygen tension but also the ΔΨ m . This may prove useful in monitoring ΔΨ m under anoxic or ischemic conditions in intact tissue.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Published by Elsevier B.V.)
Databáze: MEDLINE
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