Biogenesis of mitochondria 20 the effects of altered membrane lipid composition on mitochondrial oxidative phosphorylation inSaccharomyces cerevisiae |
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Authors: | J. M. Haslam J. W. Proudlock Anthony W. Linnane |
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Affiliation: | 1. Department of Biochemistry, Monash University, 3168, Clayton, Victoria, Australia
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Abstract: | - The lipid composition of mitochondria isolated from a fatty acid desaturase mutant ofSaccharomyces cerevisiae may be extensively manipulated by growing the organism on defined supplements of unsaturated fatty acid (UFA).
- The fatty acid composition of the mitochondrial lipids closely follows that of the whole cells from which the mitochondria are isolated. UFA-depleted mitochondria contain normal levels of sterols, neutral lipids and total phospholipids, but have much lower levels of phosphatidyl inositides.
- UFA-depleted mitochondria possess a full complement of cytochromes, oxidase both NAD-linked and flavoprotein-linked substrates at normal rates, and have levels of succinate and malate dehydrogenases similar to those of UFA-supplemented mitochondria. However, UFA-depletion has a marked effect on the ability of cytochromec to reactivate the NADH oxidase activity of cytochromec-depleted mitochondria.
- The efficiency of oxidative phosphorylation decreases progressively with the UFA content of the mitochondria, and oxidative phosphorylation is completely lost in mitochondria containing approximately 20% UFA.
- The incorporation of UFA into the lipids of UFA-depleted mitochondriain vivo results in a recoupling of oxidative phosphorylation. Recoupling is insensitive to both chloramphenicol and cycloheximide, indicating that all the proteins necessary for oxidative phosphorylation are present in UFA-depleted mitochondria, and that the less of oxidative phosphorylation is a purely lipid lesion.
- ATPase activity is apparently unaffected by UFA-depletion, but32Pi-ATP exchange activity is lost in mitochondria which have been extensively depleted in UFA.
- Valinomycin stimulates the respiration of UFA-supplemented mitochondria in media containing potassium, but has no effect on the respiration of UFA-depleted mitochondria, suggesting that active transport of potassium is lost as a result of UFA-depletion.
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