Interactions between the cytochrome pathway and the alternative oxidase in isolated Acanthamoeba castellanii mitochondria.
The steady-state activity of the two quinol-oxidizing pathways of Acanthamoeba castellanii mitochondria, the phosphorylating cytochrome pathway (i.e. the benzohydroxamate(BHAM)-resistant respiration in state 3) and the alternative oxidase (i.e. the KCN-resistant respiration), is shown to be fixed by ubiquinone (Q) pool redox state independently of the reducing substrate (succinate or exogenous reduced nicotinamide adenine dinucleotide (NADH)), indicating that the active Q pool is homogenous. For both pathways, activity increases with the Q reduction level (up to 80%). However, the cytochrome pathway respiration partially inhibited (about 50%) by myxothiazol decreases when the Q reduction level increases above 80%. The decrease can be explained by the Q cycle mechanism of complex III. It is also shown that BHAM has an influence on the relationship between the rate of ADP phosphorylation and the Q reduction level when alternative oxidase is active, and that KCN has an influence on the relationship between the alternative oxidase activity and the Q reduction level. These unexpected effects of BHAM and KCN observed at a given Q reduction level are likely due to functional connections between the two pathways activities or to protein-protein interaction.
Jarmuszkiewicz
Wieslawa
W
Department of Bioenergetics, Adam Mickiewicz University, Institute of Molecular Biology and Biotechnology, Poznan, Poland.
Sluse
Francis E
FE
Hryniewiecka
Lilla
L
Sluse-Goffart
Claudine M
CM
D000048:Acanthamoeba / Q000201:enzymology / Q000648:ultrastructure*; D000818:Animals; D003580:Cytochromes / Q000378:metabolism*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D008689:Methacrylates; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D024101:Mitochondrial Proteins; D009243:NAD / Q000494:pharmacology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010940:Plant Proteins; D013844:Thiazoles / Q000494:pharmacology; D014451:Ubiquinone / Q000378:metabolism; D000099188:Alternative Oxidase
D003580:Cytochromes; D014450:Electron Transport Complex III; D008689:Methacrylates; D024101:Mitochondrial Proteins; D009243:NAD; D010088:Oxidoreductases; D010940:Plant Proteins; D013844:Thiazoles; D014451:Ubiquinone; D000099188:Alternative Oxidase; C030517:myxothiazol