Biogenesis of mitochondria 19 the effects of unsaturated fatty acid depletion on the lipid composition and energy metabolism of a fatty acid desaturase mutant of

Abstract

Abstract1. The lipid composition of a mutant of Saccharomyces cerevisiae which cannot synthesize unsaturated fatty acid (UFA) can be extensively manipulated by growing the organism in the presence of added fatty acids.2. Growth of the mutant is supported by a wide range of unsaturated fatty acids including oleie, palmitoleic, petroselenic, l l-eicosaenoic, ricinoleic, araehidonic, clupanodonic, linoleie and linolenic acids; 9-and 10-hydroxystearic acids support growth less effectively, but erucic, nervonic, elaidic and saturated fatty acids (Cs:0-C20:0)* are ineffective. All the fatty acids which support growth are incorporated into cell lipids, apparently without further metabolism.3. The effects of altered lipid composition on the energy metabolism of yeast ceils were investigated. Cells containing less than approximately 20 % of their fatty acids as UFA cannot grow on non-fermentable substrates, and their growth on glucose is restricted to that which can be supported by fermentation alone.4. UFA-depleted cells contain mitochondria which are apparently normal in morphology, furthermore they have normal levels of cytochromes a + a3, b, cl and c and respire at normal rates. This suggests that the lesion in energy metabolism produced by UFAdepletion may be the loss of the ability of the mitochondria to couple respiration to phosphorylation.5. UFA-depleted cells incorporate added UFA into their cell lipids and subsequently regain the ability to grow on non-fermentable substrates, showing that the lesion in energy metabolism is fully reversible.

Assembly of imported subunit 8 into the ATP synthase complex of isolated yeast mitochondria

“…Liquid media contained 1% yeast extract, Sacc salts [14], appropriate auxotrophic supplements and a carbon source. Supplements of histidine (50 pg/ml) and adenine (100 yg/ml) were added to maintain the growth of J69-1B and M31; for YGL-1, histidine alone was used.…”

The manipulation of cellular cytochrome and lipid composition in a haem mutant of Saccharomyces cerevisiae

“…Total fatty acids in cells and mitochondria were analysed essentially as described by Proudlock et al (1971). Cellular and mitochondrial sterol analyses were performed on the neutral-lipid extracts by g.l.c.…”

Dietary fatty acids alter mitochondrial phospholipid fatty acyl composition and proton leak in <i>Drosophila melanogaster</i>

“…Dietary fatty acid manipulation is a wellestablished method known to alter membrane phospholipid fatty acyl profiles in several organisms. The effect of dietary fatty acids on cellular and sub-cellular membrane lipid fatty acid composition has been widely reported in cell cultures 16 , bacteria 35 , yeast 25 , insects 36 , birds 30 and mammals 32 . Dietary lipid modulates membrane lipid composition by two main mechanisms: (i) By providing the fatty acids available to be incorporated into membrane phospholipids, or (ii) By providing the precursors for other membrane lipid fatty acids.…”

“…For instance, in mitochondria, there are inconsistencies in the effect of mitochondrial phospholipid fatty acyl composition on mitochondrial respiration. While some groups reported significant changes in respiration, such as increase in membrane potential and decrease in respiratory control ratio with high membrane unsaturation 22,23 , others did not report any significant changes or reported the opposite [24][25][26] . This may partly be due to the fact that most of these studies did not measure the correct mitochondrial membrane parameters, for instance the mitochondrial membrane proton conductance, which shows significant consistent correlation with mitochondrial membrane fatty acyl composition.…”