The influence of fatty acid composition on the rate of binding of lecithin by extracted mitochondria

Abstract

1. (1)|A technique for measuring the rate of binding of lipid micelles by mitochondrial protein has been developed. 2. (2)|After an initial rapid uptake, lecithin micelles were bound by mitochondrial protein at a steady rate. With increasing concentrations of lecithin in micellar solutions this steady rate was increased towards a maximum rate. 3. (3)|These results have been interpreted as indicating that the binding was a two-step process, in which the second step was rate limiting. The first step was considered to be the collision of micelles with protein particles and the second a re-arrangement of micelles so that the lecithins formed bonds with structural protein. 4. (4)|Comparisons of the rates of binding of micelles of lecithins from normal and deficient rats has shown that fatty acid composition can influence this binding. Calculation from the experimental data showed that the maximum rate of binding of “deficient” lecithins was 2.5 to 3.0 times greater than that of “normal” lecithins. 5. (5)|These results suggest that the hydrophobic bonds between phospholipids and structural protein are influenced by fatty acid composition and that phospholipids from normal rats are bound by structural protein more slowly than are those from deficient rats. 6. (6)|It is suggested that structural protein has some special sites for hydrophobic bonding of arachidonic acid, in which phospholipids containing arachidonic acid are bound more slowly but also more firmly than other phospholipids. This could explain the reported fragility of lipoprotein membranes in animals deficient in essential fatty acids.