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(28) Ca2+ -BINDING PROPERTIES OF LONG-CHAIN SATURATED FATTY ACIDS AND THEIR POSSIBLE ROLE IN MITOCHONDRIA G.D. Mironova1, O.
Gateau-Roesch2, C. Levrat2, E. Pavlov1,
A.V. Lazareva3, E. Limarenko3, C. Rey2
and N-E.L. Saris4
The Ca2+-binding properties of different lipids have been studied. It was found that saturated fatty acids (FA) had higher Ca2+-binding than unsaturated FA, phospholipids, and lysophospholipids. The Ca2+-binding varied with the length of the aliphatic chain of FA; palmitic, stearic and eicosanoic acids exhibited the highest Ca2+-binding. For palmitic and stearic acids, the Kd for Ca2+ were 5 mM at pH 8.5 and 15 mM at pH 7.5, with a Bmax of 0.48 + 0.08 mmol/g. This corresponds to one Ca2+ for eight palmitic or stearic acid molecules. The data of IR-spectroscopy confirm that Ca2+ does not form ionic bonds with palmitic and stearic acids under hydrophobic conditions. Ca2+-binding was inhibited by Mg2+ but not by K+. The Ca2+-binding was mainly located in the contact site-enriched fraction. Palmitic and stearic acids incorporated into a black-lipid membrane (BLM), induced channel activity in presence of Ca2+. KCL increased the permeabilily of this BLM, but only in presence of Ca2+. The unsaturated palmitoleic and oleic acids, that does not bind Ca2+ with high affinity, showed no changes in permeability of the membrane in presence of Ca2+ and K+. Incubation of mitochondria with Ca2+ to induce a permeability transition, increased the extractable amounts of palmitic and stearic acids, this effect was prevented by phospholipase A2 inhibitors. The involvement of the long-chain FA in the mitochondrial permeability transition is discussed.
For further information contact...Carmen Mannella: carmen@wadsworth.org |
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