Molecular control of membrane properties during temperature acclimation. Membrane fluidity regulation of fatty acid desaturase action?

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Abstract
Further studies on the molecular mechanisms of temperature acclimation were carried out using the ciliate Tetrahymena pyriformis. The most prominent change in lipid metabolism during acclimation to high temperature.sbd. depression of fatty acid desaturase activity.sbd. could be simulated by supplementing the growth medium of isothermally-grown cells with polyunsaturated fatty acids. Such cells resisted the membrane-fluidizing effect of the incorporated exogenous acids by increased use of de novo synthesized saturated acids in their phospholipids. The data support the conclusions arising from earlier experiments with temperature-shifted cells (Martin, et al 1976), showing that when membrane fluidity increased to a superoptimal level, the activity of membrane-associated fatty acid desaturases decreased. Since the reaction was controlled by membrane fluidity rather than temperature this seems to be the general mechanism employed by cells adjusting to any fluidity-modifying factor, such as cations, drugs, etc.