Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Host organism: Homo sapiens
Associated disease: diarrhea [ICD11:
ME05.1 
, ICD11:
SA55 ];
infection due to Escherichia coli [ICD11:
XN6P4 ]
NCBI PubMed ID: 28609625Publication DOI: 10.1021/acs.biochem.7b00106Journal NLM ID: 0370623Publisher: American Chemical Society
Correspondence: wonpil
lehigh.edu; goran.widmalm
su.se
Institutions: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden, Department of Biological Sciences and Bioengineering Program, Lehigh University , Bethlehem, Pennsylvania 18015, United States
The outer leaflet of the outer membrane in gram-negative bacteria contains lipopolysaccharides (LPS) as a major component, and the outer membrane provides a physical barrier and protection against hostile environments. The enterohemorrhagic E. coli of serogroup O91 has an O-antigen polysaccharide (PS) with five sugar residues in the repeating unit (RU) and the herein studied O-antigen PS contains ~10 RUs. 1H,13C-HSQC-NOESY experiments on a [1-13C]-labeled PS were employed to deduce 1H,1H cross-relaxation rates and transglycosidic 3JCH related to the torsional angles. Dynamical parameters were calculated from the molecular dynamics (MD) simulations of the PS in solution and compared to those from 13C NMR relaxation studies. Importantly, the MD simulations are able to reproduce dynamical behavior of internal correlation times along the PS chain. Two-dimensional free energy surfaces of glycosidic torsion angles delineate the conformational space available to the O-antigen. Although similar with respect to populated states in solution, the O-antigen in LPS bilayers have more extended chains as a result of spatial limitations due to close packing. Calcium ions are highly abundant in the phosphate-containing core region mediating LPS-LPS association crucial for maintaining bilayer integrity, and the negatively charged O-antigen promotes a high concentration of counterbalancing potassium ions. The ensemble of structures present for the PS in solution are captured by the NMR experiments and the similarities between the O-antigen on its own and as a constituent of the full LPS in bilayer environment makes it possible to realistically describe the LPS conformation and dynamics from the MD simulations.
Lipopolysaccharide, conformation, O-antigen, Escherichia coli, molecular dynamics, NMR spectroscopy, gram negative bacteria, simulation, outer membrane, bilayer
Structure type: polymer biological repeating unit ; n=10
Location inside paper: p.3827, fig.1
Compound class: 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
Methods: 13C NMR, 1H NMR, NMR-2D, MD simulations, computation of NMR relaxation parameters
3D data: conformation analysis
NCBI Taxonomy refs (TaxIDs): 1055539
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There is only one chemically distinct structure:
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