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References to other databases: GTC:G98477AV, GlycomeDB:3543
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

The factors responsible for serotype 1a O-antigen modification in Shigella flexneri were localized to a 5.8-kb chromosomal HindIII fragment of serotype 1a strain Y53. The entire 5.8-kb fragment and regions up- and downstream of it (10.6-kb total) were sequenced. A putative three-gene operon, which showed homology with other serotype conversion genes, was identified and shown to confer serotype 1a O-antigen modification. The serotype conversion genes were flanked on either side by phage DNA. Multiple insertion sequence (IS) elements were located within and upstream of the phage DNA in a composite transposon-like structure. Host DNA homologous to the dsdC and the thrW proA genes was located upstream of the IS elements and downstream of the phage DNA, respectively. The sequence analysis indicates that the organization of the 10.6-kb region of the Y53 chromosome is unique and suggests that the serotype conversion genes were originally brought into the host by a bacteriophage. Several features of this region are also characteristic of pathogenicity islands.

gene, characterization, serotype, O-antigen, molecular, Shigella flexneri, modification, Shigella, chromosome

NCBI PubMed ID: 10419979
Journal NLM ID: 2985120R
Publisher: American Society for Microbiology
Correspondence: Naresh.Verma@anu.edu.au
Institutions: Division of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia

The genes encoding type IV O antigen glucosylation were characterized from both Escherichia coli and Shigella flexneri. The putative O antigen modification genes from E. coli, o120 o306 o443, were PCR-amplified and introduced into S. flexneri serotype Y strain SFL124. Immunogold labelling and phage sensitivity indicated the presence of both serotype Y and serotype 4a O antigens on the cell surface of the resulting recombinant SFL124 strains, suggesting that only partial serotype conversion was conferred by the E. coli genes. The type IV O antigen modification genes were then isolated and characterized from S. flexneri serotype 4a strain NCTC 8296. A 3.8 kb chromosomal fragment conferred complete conversion to serotype 4a when introduced into SFL124. Sequence analysis of the fragment revealed the presence of three genes, gtrA(IV) gtrB(IV) gtrIV(Sf). DNAs homologous to bacteriophage int and attP were located upstream of gtrA(IV), suggesting that this region of the NCTC 8296 genome may have originated from a bacteriophage; however, a serotype-converting phage could not be induced from this strain nor from other strains used in this study. Comparison of the GtrIV(Sf) and GtrIV(Ec) (o443) proteins revealed that they are 41% identical and 63% similar, which is the highest degree of similarity reported among the S. flexneri O antigen glucosyltransferases.

Lipopolysaccharide, antigen, gene, O-antigen, Shigella flexneri, type, modification, glucosyltransferase, genome, bacteriophage, serotype conversion

NCBI PubMed ID: 11283281
Publication DOI: 10.1099/00221287-147-4-851
Journal NLM ID: 0376646
Publisher: Washington, DC: Kluwer Academic/Plenum Publishers
Correspondence: Naresh.Verma@anu.edu.au
Institutions: Division of Biochemistry and Molecular Biology, School of Life Sciences, Faculty of Science, The Australian National University, Canberra, Australia

An acidic O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Escherichia coli O150 and studied by sugar and methylation analyses, tri?ic acid solvolysis, Smith degradation, 1H and 13C NMR spectroscopy, including 2D ROESY, 1H,13C HSQC, HMQC-TOCSY, and HMBC experiments. The polysaccharide was found to contain a regioisomer of N-acetylisomuramic acid, 2-acetamido-4-O-[(S)-1-carboxyethyl]-2-deoxy-D-glucose [D-GlcNAc4(Slac)]. The structure of its hexasaccharide repeating unit was established.

O-antigen, Escherichia coli, teichoic acid, O-Polysaccharide structure, 2-Acetamido-4-O-[(S)-1-carboxyethyl]-2-deoxy-D-glucose, Trific acid solvolysis

NCBI PubMed ID: 16997291
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: perepel@ioc.ac.ru
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia,TEDA School of Biological Sciences and Biotechnology, Nankai University, 23 HongDa Street, TEDA, Tianjin, China,Tianjin Key Laboratory for Microbial Functional Genomics, TEDA College, Nankai University, 23 HongDa Street, TEDA,Tianjin, China
Methods: 13C NMR, 1H NMR, NMR-2D, methylation, GLC-MS, chemical analysis, ESI-MS, GLC, mild acid hydrolysis, Smith degradation, NMR-1D, triflic acid solvolysis

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.