The effect of aliphatic alcohols upon the dissociation of micrococcus lysodeikticus membrane lipids and proteins

Abstract

The ability of aliphatic alcohols to extract 32P-labeled phospholipid from aqueous dispersions of Micrococcus lysodeikticus membranes into the organic solvent phase has been investigated and the following order of efficiency of extraction observed: tert-amyl alcohol = n-butanol = iso-butanol = sec-butanol > n-amyl alcohol > iso-amyl alcohol > 3-pentanol. This order approximates that of the water solubility of these alcohols. Inclusion of urea (2 M or 6 M) or NaCl (0.1 M or 1.0 M) in the aqueous phase reduced the extractibility of 32P-labeled lipid into the organic solvent phase. Residual 32P-labeled material in the aqueous phase following n-butanol extraction could in part be accounted for as phospholipid. Almost maximal recovery of the phospholipid in the solvent phases occurred when aqueous dispersions of membrane lipid and bovine serum albumin (protein: lipid ratio, 2:1) were extracted. The recovery of protein in the aqueous phase was about 45–50 % for all solvents and thus represents a much lower value for “soluble” protein than that observed with erythrocyte membranes. The lower recovery of soluble proteins in this bacterial membrane system is probably due to the presence of insoluble aggregates of the electron transport components of the membrane. Addition of 2 M urea increased solubilization of protein, whereas 6 M urea and 0.1 and 1.0 M NaCl decreased the aqueous phase protein. ATPase activity survived extraction with a number of the alcohols, being less sensitive to those with the hydroxyl group on carbon-1; it was largely inactivated by urea and NaCl additions to the aqueous phase. NADH-dehydrogenase showed good preservation following extraction with tert-amyl alcohol in the presence of 2 M urea.