Abstract
A previous report from this laboratory (van Golde, L.M.G., Schulman, H., and Kennedy, E.P. (1973) Proc. Natl. Acad. Sci. U.S.A. 70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage. These membrane-derived oligosaccharides, comprising about 0.5 to 1.0% of the dry weight of E. coli, represent a family of closely related oligosaccharides that may be subfractionated on anion exchange resins. The present paper describes studies of the oligosaccharide A-1 described by van Golde et al. in the previous report. The glycerophosphate linked to the oligosaccharide in phosphodiester bond is the sn-glycero-1-P enantiomer. This finding strongly supports the previous conclusion that the oligosaccharides are the acceptors of the polar headgroups of membrane phospholipids, since the unesterified glycerophosphate of phosphatidyl glycerol is an sn-glycero-1-P residue, otherwise rare in nature. The glycerophosphate residues in the membrane-derived oligosaccharide are not substituted in the sn-2 or sn-3 positions, since they are readily oxidized by periodate under mild conditions. Alkaline hydrolysis liberates glycerophosphate, and only negligible amounts of free glycerol, consistent with the view that the glycerophosphate residues are linked to glucose units through position 6, unfavorable for the formation of glucose cyclic phosphate intermediates that would eliminate free glycerol. Oligosaccharide A-1 (but not Fraction A-2) contains phosphoethanolamine residues equivalent to 30 to 40% of the total phosphorus. The phosphoethanolamine residues are linked to position 6 of glucose units, as proved by the isolation of glucose 6-phosphate as a product of partial acid hydrolysis.
Highlights
A. 70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage
Isolation of a- and P-Glycerophosphates as Products of Alkaline Hydrolysis-A sample of Fraction A-l containing 11.8 pmol of total phosphorus was hydrolyzed in 0.5 ml of 0.5 N
The alkaline hydrolysis of phosphodiester derivatives of glycerol, in a reaction in which negligible amounts of free glycerol are produced, undoubtedly involves the formation of glycero-1(3),2-cyclic phosphate as intermediate. Such cyclic phosphates are unstable in alkali and are cleaved to give a mixture of the phosphomonoesters glycero-1(3)-P and glycero-2-P
Summary
70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage. A. 70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage These membrane-derived oligosaccharides, comprising about 0.5 to 1.0% of the dry weight of E. coli, represent a family of closely related oligosaccharides that may be subfractionated describes studies of the oligosaccharide. The glycerophosphate linked to the oligosaccharide in phosphodiester bond is the sn-glycero-1-P enantiomer This finding strongly supports the previous conclusion that the oligosaccharides are the acceptors of the polar headgroups of membrane phospholipids, since the unesterified glycerophosphate of phosphatidylglycerol is an sn-glycero-1-P residue, otherwise rare in nature. The membrane-derived oligosaccharides constitute-a closely [1] revealed that szP is continuously lost from phosphatidylrelated family of compounds
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