EFFECTS OF MEMBRANE-LIPID COMPOSITION ON NASCENT PROTEIN TRANSLOCATION INDUCED BY HEAT AND ETHANOL IN ESCHERICHIA-COLI

1. In fatty acid supplemented E. coli auxotrophs the degree of saturat ion in acyl chains 18 carbons long did not influence the translocation of protein to the outer membrane under hyperthermal stress. However, in cells grown in medium supplemented with 20-carbon fatty acids the d egree of saturation markedly affected protein translocation and acute exposure of cells to 6% (v/v) ethanol mimicked the effects of hyperthe rmic treatment. 2. P-31 NMR studies revealed that whole membranes exhi bited lamellar properties at 25 degrees C but at growth temperature (3 9 degrees C) and above they exhibited a mainly isotropic nature irresp ective of fatty acid supplement. At temperatures greater than 40 degre es C, a new isotropic component (ca 20 ppm downfield) was observed. Th is isotropic component does not appear to arise from any typical phosp horus metabolite or lipid phase. 3. The role of lipid composition in p rotein translocation induced by ethanol and heat stress are discussed and a hypothesis for heat shock activation is presented.