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Found 1 structure.
Displayed structure 1
| R-3HOBut-(1-3)-+ Gly-(2-6)-+ | | -4)-a-D-Quip3N-(1-4)-b-D-Galp-(1-4)-b-D-GlcpNAc-(1-4)-b-D-GlcpA-(1-3)-b-D-GlcpNAc-(1- | Show graphically |
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Structure type: suggested polymer biological repeating unit
Compound class: O-polysaccharide, O-antigen
Contained glycoepitopes: IEDB_115136,IEDB_130646,IEDB_135813,IEDB_136044,IEDB_137340,IEDB_137472,IEDB_140108,IEDB_140122,IEDB_140630,IEDB_141794,IEDB_141807,IEDB_151527,IEDB_151531,IEDB_190606,IEDB_423153,SB_165,SB_166,SB_187,SB_195,SB_30,SB_7,SB_88
The dynamics of the O-antigen part of the lipopolysaccharide from the enterohemorrhagic Escherichia coli O91 has been determined in solution using (13)C NMR relaxation measurements at two magnetic field strengths,9.4 and 14.1 T, thereby facilitating the testing of several dynamical models. The biological repeating unit, consisting of five sugar residues and substituents, could be determined by spectral analysis of different (1)H,(13)C correlations and corroborated by the relaxation data. The site specifically (13)C-labeled material was shown to have approximately 10 repeating units with a narrow distribution. A model-free analysis of the relaxation data revealed a complex dynamical behavior where the sugar residues could be described by a global correlation time (tau(m) = 5.4 ns), generalized order parameters (S(2) approximately 0.63), and different correlation times for internal motions related to their position in the repeating unit along the polymer (tau(e) approximately 360-520 ps). One of the sugar residues showed, in addition, a chemical exchange contribution. Furthermore, a substituent on another sugar residue was described by two order parameters (S(f)(2) = 0.51 and S(s)(2) = 0.21). The solution dynamics of the polysaccharide are thus described by highly intricate motions, both in amplitude and time scales. These results are of significance in the general description of polysaccharides surrounding bacterial cell surfaces and in the presentation of antigenic epitopes to the immune system of an invaded host.
Lipopolysaccharide, NMR, chemistry, correlation, Bacterial, host, significance, polysaccharide, O-antigen, repeating unit, analysis, O antigen, cell, polymer, Escherichia, Escherichia coli, epitope, complex, epitopes, dynamics, biological, chemical, sugar, polysaccharides, position, surface, antigenic, time, site, measurement, solution, relaxation, distribution, exchange, organic, antigenic epitopes, behavior, biological repeating unit, chemical exchange, enterohemorrhagic, immune, immune system, internal motion, model, models, motion, order, presentation
NCBI PubMed ID: 15132695The structure of the O-antigenic polysaccharide from the enterohemorrhagic Escherichia coli O91 has been determined using primarily NMR spectroscopy on the (13)C-enriched polysaccharide. The O-antigen is composed of pentasaccharide repeating units with the following structure: →4)-β-D-Galp-(1→4)-β-D-GlcpNAc-(1→4)-β-D-GlcpA-6-N-Gly-(1→3)-β-D-GlcpNAc-(1→4)-α-D-Quip-3-N-[(R)-3-hydroxy butyra mido]-(1→. The bacterium was grown with D-[UL-(13)C]glucose in the medium which resulted in an overall degree of labeling of approximately 65% in the sugar residues and approximately 50% in the N-acyl substituents, indicating some metabolic dilution in the latter. The (13)C-enrichment of the polysaccharide proved valuable since NMR assignments could be made on the basis of (13)C, (13)C-connectivity in uniformly labeled residues. The biosynthesis of the (R)-3-hydroxybutyramido substituent via C(2) fragments was identified by NMR spectroscopy. The (R)-configuration at C3 is in accord with fatty acid biosynthesis. Additional cultures with specifically labeled D-[1-(13)C]glucose or D-[6-(13)C]glucose corroborated the direct incorporation of glucose as the building block for the hexose skeletons in the polysaccharide and the biosynthesis of acyl substituents occurring via the triose pool followed by decarboxylation to give acetyl building blocks labeled with (13)C at the methyl group.
NMR, biosynthetic, structural, polysaccharide, Escherichia, Escherichia coli, determination, O-antigenic, O-antigenic polysaccharide, structural determination, NMR spectroscopy, spectroscopy, antigenic, enterohemorrhagic
NCBI PubMed ID: 10493787Escherichia coli is usually a non-pathogenic member of the human colonic flora. However, certain strains have acquired virulence factors and may cause a variety of infections in humans and in animals. There are three clinical syndromes caused by E. coli: (i) sepsis/meningitis; (ii) urinary tract infection and (iii) diarrhoea. Furthermore the E. coli causing diarrhoea is divided into different 'pathotypes' depending on the type of disease, i.e. (i) enterotoxigenic; (ii) enteropathogenic; (iii) enteroinvasive; (iv) enterohaemorrhagic; (v) enteroaggregative and (vi) diffusely adherent. The serotyping of E. coli based on the somatic (O), flagellar (H) and capsular polysaccharide antigens (K) is used in epidemiology. The different antigens may be unique for a particular serogroup or antigenic determinants may be shared, resulting in cross-reactions with other serogroups of E. coli or even with other members of the family Enterobacteriacea. To establish the uniqueness of a particular serogroup or to identify the presence of common epitopes, a database of the structures of O-antigenic polysaccharides has been created. The E. coli database (ECODAB) contains structures, nuclear magnetic resonance chemical shifts and to some extent cross-reactivity relationships. All fields are searchable. A ranking is produced based on similarity, which facilitates rapid identification of strains that are difficult to serotype (if known) based on classical agglutinating methods. In addition, results pertinent to the biosynthesis of the repeating units of O-antigens are discussed. The ECODAB is accessible to the scientific community at http://www.casper.organ.su.se/ECODAB/
NMR, structure, serotype, O-antigen, Enterobacteriacea, database
NCBI PubMed ID: 16594963In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of 13C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly 13C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-13C)-sucrose, 342 Da] and one compound of medium molecular weight (13C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The 13C resonances are traced using 13C-13C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the 13C resonances, the 1H chemical shifts are derived in a straightforward manner using one-bond 1H-13C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the 1 J CC splitting of the 13C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either 13C or 1H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the 1H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the 13C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with 15N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and 13C-detected (H)CACO spectra.
NMR, carbohydrates, structure, Escherichia coli, Structure determination, 13C-uniform labeling
NCBI PubMed ID: 24771296Escherichia coli includes clonal groups of both commensal and pathogenic strains, with some of the latter causing serious infectious diseases. O antigen variation is current standard in defining strains for taxonomy and epidemiology, providing the basis for many serotyping schemes for Gram-negative bacteria. This review covers the diversity in E. coli O antigen structures and gene clusters, and the genetic basis for the structural diversity. Of the 187 formally defined O antigens, six (O31, O47, O67, O72, O94 and O122) have since been removed and four (O14, O34, O89 and O144) strains do not produce any O antigen. Therefore, structures are presented for 176 of the 181 E. coli O antigens, some of which include subgroups. Most (93%) of these O antigens are synthesized via the Wzx/Wzy pathway, 11 via the ABC transporter pathway, with O20, O57 and O60 still uncharacterized due to failure to find their O antigen gene clusters. Biosynthetic pathways are given for 38 of the 49 sugars found in E. coli O antigens, and several pairs or groups of the E. coli antigens that have related structures show close relationships of the O antigen gene clusters within clades, thereby highlighting the genetic basis of the evolution of diversity.
structure, O antigen, Escherichia coli, gene cluster, serogroup, diversity
NCBI PubMed ID: 31778182| New query | Export IDs | Home | Help |
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