Structural studies of the membrane-derived oligosaccharides of Escherichia coli.

J.E Schneider,V Reinhold,M.K Rumley,E.P Kennedy

doi:10.1016/s0021-9258(19)86683-8

Abstract

Membrane-derived oligosaccharides are a novel class of glucose-containing oligosaccharides found in the cell envelope of Escherichia coli and other Gram-negative organisms (Schulman, H., AND Kennedy, E.P. (1979) J. Bacteriol. 137, 686-688). Previous work has shown that these oligosaccharides contain sn-1-glycero-P and smaller amounts of phosphoethanolamine, derived from membrane phospholipids, attached to position 6 of certain of the glucose residues. The structure of the parent oligosaccharides (obtained by reduction with borohydride followed by alkaline hydrolysis) has now been studied. The oligosaccharide was permethylated, followed by hydrolysis and conversion of the products to methylated glucitol acetates, which were then analyzed and identified by gas-liquid chromatography and mass spectrometry. The membrane oligosaccharides contain 10 to 12 D-glucopyranoside residues/mol, linked solely by 1 yields 2 and 1 yields 6 bonds. They are highly branched structures, with four nonreducing termini per mol. Glucose units at the branch points are doubly substituted at positions 2 and 6. The low specific rotation of the oligosaccharide (+8.3 degrees) indicates that the glycosidic bonds are predominantly or entirely beta.

Highlights

Membrane-derived oligosaccharides are a novel class of glucose-containing oligosaccharides found in the cell envelope of Escherichia coli and other Gram-negative organisms
The membrane-derived oligosaccharides (MDO’) of Escherichia coli constitute a closely related family of compounds containing glucose as the sole sugar, substituted with sn-lglycerophosphate and smaller amounts of phosphoethanolamine residues in phosphodiester linkage [1, 2]. These substituents are derived from the polar head groups of membrane phospholipids of E. coli which are continuously transferred to these oligosaccharides, accounting for about 90% of the observed turnover of the membrane phospholipids [3]
Since the membrane-derived oligosaccharides of E. coli constitute a family of closely related species varying in net negative charge, the possibility must be considered that the oligosaccharide moiety of the MD0 may be variable, as well as the pattern of substitution

Summary

Introduction

Membrane-derived oligosaccharides are a novel class of glucose-containing oligosaccharides found in the cell envelope of Escherichia coli and other Gram-negative organisms The membrane-derived oligosaccharides (MDO’) of Escherichia coli constitute a closely related family of compounds containing glucose as the sole sugar, substituted with sn-lglycerophosphate and smaller amounts of phosphoethanolamine residues in phosphodiester linkage [1, 2]. These substituents are derived from the polar head groups of membrane phospholipids of E. coli which are continuously transferred to these oligosaccharides, accounting for about 90% of the observed turnover of the membrane phospholipids [3].

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Conclusion