CRYO-TEM AND NMR-STUDIES OF A MICELLE-FORMING PHOSPHOGLUCOLIPID FROM MEMBRANES OF ACHOLEPLASMA-LAIDLAWII-A AND ACHOLEPLASMA-LAIDLAWII-B

The chemical structure of a phosphoglucolipid from the membrane of the bacterium Acholeplasma laidlawii strain B-PG9 has been determined by high resolution NMR to be -[glycerophosphoryl-6-O-(alpha-D-glucopyrano syl-(1 --> 2)-O-alpha-D-glucopyranosyl)]-sn-glycerol (GPDGlcDAG). It w as concluded that this lipid has exactly the same structure as one of the phosphoglucolipids from A. laidlawii strain A-EF22. By cryo transm ission electron microscopy (cryo-TEM) and NMR diffusion techniques it was shown that, in highly diluted aqueous solutions, this membrane lip id forms long thread-like micelles in equilibrium with lipid vesicles. The cause of the occurrence of these different aggregates is discusse d in terms of the varying molecular shapes of the lipid because of a h eterogeneous composition of the acyl chains. A second membrane phospho glucolipid from the bacterium, namely -[glycerophosphoryl-6-O-(alpha-D -glucopyranosyl-(1 --> hosphoryl-6-O-alpha-D-glucopyranosyl)]-sn-glyce rol (MABGPDGlcDAG), was found to form only a lamellar liquid crystalli ne phase coexisting with water. Copyright (C) 1997 Elsevier Science Ir eland Ltd.