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The O-polysaccharide (O-antigen) of Escherichia coli O43 was isolated from the lipopolysaccharide and studied by chemical methods, including sugar analyses, Smith degradation, and solvolysis with anhydrous trifluoroacetic acid, along with (1)H and (13)C NMR spectroscopy. The following structure of the pentasaccharide repeating unit of the O-polysaccharide was established: Functions of genes in the O-antigen gene cluster of E. coli O43 were assigned by a comparison with sequences in the available databases and found to be in agreement with the O-polysaccharide structure.

Lipopolysaccharide, O-antigen, Escherichia coli, bacterial polysaccharide structure, O-antigen gene cluster

NCBI PubMed ID: 26342864
Publication DOI: 10.1016/j.carres.2015.08.008
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: perepel@ioc.ac.ru (A. V. Perepelov)
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, TEDA Institute of Biological Sciences and Biotechnology, TEDA, Nankai University, 300457 Tianjin, China
Methods: 13C NMR, 1H NMR, NMR-2D, de-O-acylation, sugar analysis, GLC, mild acid hydrolysis, Smith degradation, NMR-1D, GPC, bioinformatic analysis, solvolysis with CF3CO2H

This review is devoted to methods for the selective cleavage of glycosidic bonds. The mechanisms of reactions underlying these methods are considered and examples of their practical application in the structural analysis of bacterial polysaccharides are given. Specific methods for the selective cleavage of polysaccharides, remaining relevant for researchers, include the Smith degradation based on destruction of monosaccharides containing vicinal diol groups, dephosphorylation of phosphate-containing polysaccharides with hydrofluoric acid and the hydrolytic cleavage of glycosyl phosphate bonds in the latter compounds. Non-specific methods, including partial acid hydrolysis, acetolysis and solvolysis with anhydrous organic (CF3SO3H, MeSO3H, CF3CO2H) and inorganic (HF) acids do not make any specific demands on the composition and structure of the polysaccharide and are sensitive to its fine structural features. The review addesses the issue of stability of glycosidic bonds in various monosaccharides to reagents used for non-specific selective cleavage.

structural analysis, Bacterial polysaccharide, selective cleavage, glycosidic bond

Publication DOI: 10.1070/RCR4856
Journal NLM ID: 0404506
Publisher: London: Chemical Society
Correspondence: Yu.A. Knirel
Institutions: N.D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences
Methods: partial acid hydrolysis, HF solvolysis, acid hydrolysis, mild acid hydrolysis, alkaline degradation, b-elimination, Smith degradation, deamination, de-O-acetylation, HF treatment, reduction with NaBD4, triflic acid solvolysis, acetolysis, Li/ethylenediamine degradation, hydrazinolysis, reduction with NaBH4, mild acid degradation, trifluoroacetic acid solvolysis, partial solvolysis with anhydrous trifluoroacetic acid, de-N-acetylation with hydrazine, part acid hydrolysis, HF solvolysis; published polymerization frame was shifted for conformity with other records.

Escherichia 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
Publication DOI: 10.1093/femsre/fuz028
Journal NLM ID: 8902526
Publisher: Oxford University Press
Correspondence: G. Widmalm ; Lei Wang
Institutions: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, China, The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, China, School of Molecular and Microbial Bioscience (G08), University of Sydney, Sydney, Australia, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China, Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China