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Found 1 structure.
Displayed structure 1
| b-D-GlcpNAc-(1-3)-+ | -2)-a-L-Rhap-(1-6)-a-D-GalpNAc-(1-4)-a-D-GalpNAc-(1-3)-a-D-GalpNAc-(1- | Show graphically |
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Structure type: suggested polymer biological repeating unit
Trivial name: O-polysaccharide
Compound class: O-polysaccharide, O-antigen
Contained glycoepitopes: IEDB_130648,IEDB_135813,IEDB_136105,IEDB_137340,IEDB_137473,IEDB_1391961,IEDB_1391965,IEDB_141582,IEDB_141584,IEDB_141807,IEDB_151531,IEDB_225177,IEDB_423113,IEDB_885822,IEDB_885823
The polysaccharide part of the lipopolysaccharide obtained from the enteropathogenic Escherichia coli O142 has been isolated, and its structure determined. Together with 1H NMR and 13C NMR spectroscopy, sugar and methylation analyses show that the polysaccharide is composed of repeating pentasaccharide units. Sequential information on the O-polysaccharide was obtained by two-dimensional NMR techniques, namely heteronuclear-multiple-bond-connectivity and NOESY experiments. The repeating unit of the O-polysaccharide of E. coli strain O142 has the following structure: [structure: see text].
NMR, structure, structural, polysaccharide, analysis, Escherichia, Escherichia coli, O-antigenic, O-antigenic polysaccharide, O-polysaccharide, structural analysis, enteropathogenic
NCBI PubMed ID: 9119011Conformational studies have been performed of a pentasaccharide derived from the O-polysaccharide from Escherichia coli O142. The polymer was selectively degraded by anhydrous hydrogen fluoride and reduced to yield an oligosaccharide model of its repeating unit, which in the branching region consists of four aminosugars. A comparison of (1)H and (13)C chemical shifts between the pentasaccharide and the polymer showed only minor differences, except where the cleavage had taken place, indicating that the oligomer is a good model of the repeating unit. Langevin dynamics and molecular dynamics simulations with explicit water molecules were carried out to sample the conformational space of the pentasaccharide. For the glycosidic linkages between the hexopyranoside residues, small but significant changes were observed between the simulation techniques. One-dimensional (1D) (1)H,(1)H double pulsed field gradient spin echo (DPFGSE) transverse rotating- frame Overhauser effect spectroscopy (T-ROESY) experiments were performed, and homonuclear cross-relaxation rates were obtained. Subsequently, a comparison of interproton distances from NMR experiment and the two simulation approaches showed that in all cases the use of explicit water in the simulations resulted in better agreement. Hydrogen-bond analysis of the trajectories from the molecular dynamics simulation revealed interresidue interactions to be important as a cluster of different hydrogen bonds and as a distinct highly populated hydrogen bond. NMR data are consistent with the presence of hydrogen bonding within the model of the repeating unit
NMR, oligosaccharide, structure, chemistry, polysaccharide, O-antigen, repeating unit, analysis, O antigen, hydrogen, hydrogen bond, molecular, molecule, polymer, water, Escherichia, Escherichia coli, glycosidic linkage, conformational, dynamics, molecular dynamics, NMR spectroscopy, cluster, O-polysaccharide, O polysaccharide, linkage, chemical, region, reduced, spectroscopy, interaction, difference, pentasaccharide, comparison, solution, case, change, simulation, effect, Overhauser effect, organic, model, use, cleavage, approach, chemical shift, chemical shifts, distance, Hydrogen Bonding, hydrogen fluoride, Langevin dynamics, rotating frame, shift
NCBI PubMed ID: 12124846Escherichia 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: 31778182Glycans, carbohydrate molecules in the realm of biology, are present as biomedically important glycoconjugates and a characteristic aspect is that their structures in many instances are branched. In determining the primary structure of a glycan, the sugar components including the absolute configuration and ring form, anomeric configuration, linkage(s), sequence, and substituents should be elucidated. Solution state NMR spectroscopy offers a unique opportunity to resolve all these aspects at atomic resolution. During the last two decades, advancement of both NMR experiments and spectrometer hardware have made it possible to unravel carbohydrate structure more efficiently. These developments applicable to glycans include, inter alia, NMR experiments that reduce spectral overlap, use selective excitations, record tilted projections of multidimensional spectra, acquire spectra by multiple receivers, utilize polarization by fast-pulsing techniques, concatenate pulse-sequence modules to acquire several spectra in a single measurement, acquire pure shift correlated spectra devoid of scalar couplings, employ stable isotope labeling to efficiently obtain homo- and/or heteronuclear correlations, as well as those that rely on dipolar cross-correlated interactions for sequential information. Refined computer programs for NMR spin simulation and chemical shift prediction aid the structural elucidation of glycans, which are notorious for their limited spectral dispersion. Hardware developments include cryogenically cold probes and dynamic nuclear polarization techniques, both resulting in enhanced sensitivity as well as ultrahigh field NMR spectrometers with a 1H NMR resonance frequency higher than 1 GHz, thus improving resolution of resonances. Taken together, the developments have made and will in the future make it possible to elucidate carbohydrate structure in great detail, thereby forming the basis for understanding of how glycans interact with other molecules.
NMR, glycan
NCBI PubMed ID: 36622423| New query | Export IDs | Home | Help |
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