Abstract
The structure of heparosan capsular polysaccharide (CPS) has been determined using enzymatic digestion with nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. Previous errors in the assignment of the glycolipid acceptor structure, from which heparosan is extended, have been corrected. The structure of heparosan CPS is GlcNAc α-1,[4GlcA β-1,4GlcNAc α-1,]n4GlcA β-1,[4Kdo β-2,7Kdo β-2,]0 or 14Kdo β-2,7Kdo β-2,4Kdo β-2,7Kdo β-2,4Kdo β-2,7Kdo β-2,4Kdo β-PG-I (C16:0 or C18:0) (where n is ~250 for a CPS of 100 kDa).
Highlights
A polysaccharide capsule, anchored in their outer cell membrane, surrounds Gram-negative bacteria, such as Escherichia coli [1]
The study clarified that the glycolipid terminus of Escherichia coli K5 heparosan is composed of several linearly linked 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) residues with a phosphatidylglycerol and monoacyl or diacyl fatty acids [7]
Heparosan disaccharide (∆UA-GlcNAc) and tetrasccharide (∆UA-GlcNAc-glucuronic acid (GlcA)-GlcNAc) standard were obtained from heparin lyase III digestion of heparosan capsular polysaccharide (CPS). 1 kDa molecular weight cut-off (MWCO) spin columns were purchased from MilliporeSigma (Burlington, MA, USA)
Summary
A polysaccharide capsule, anchored in their outer cell membrane, surrounds Gram-negative bacteria, such as Escherichia coli [1]. The CPS of Escherichia coli K5, has the repeating structure →4)-β-d-glucuronic acid (GlcA) (1→4)-α-N-acetyld-glucosamine (GlcNAc) Base hydrolysis of N-acetyl groups and their subsequent N-sulfonation are used to prepare N-sulfoheparosan from heparosan By controlling these reactions, hybrid structures, common to heparan sulfate and heparin, can be prepared. Hybrid structures, common to heparan sulfate and heparin, can be prepared These two kinds of glycosaminoglycans primarily differ by their ratio of GlcNAc and N-sulfoglucosamine (GlcNS) residues [11], and contain different contents of other frequent modifications, including epimerization of GlcA to iduronic acid (IdoA) and O-sulfation of the 2-position of IdoA residues and the 6-position of the GlcNAc or GlcNS residues. Carbohydrate-containing macromolecules of bacterial cell surfaces are important in host–pathogen interactions [13], and when their structure is known can be successfully used to prepare vaccines targeting pathogens [14]
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