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References to other databases: GTC:G34479NH, GlycomeDB:26197
Structural formula & atomic coordinates
Sweet-II 3D model
Show glycosyltransferases

We previously reported that the serotype b antigen of Actinobacillus actinomycetemcomitans is a constituent of the polysaccharide region of lipopolysaccharide (LPS) and contains significant amount of the neutral sugars rhamnose and fucose (M. Wilson and R. Schifferle, Infect. Immun. 59:1544-1551, 1991). In the present study, we determined the structure of the O antigen of A. actinomycetemcomitans Y4 (serotype b) LPS. Aqueous phase LPS was obtained from a phenol-water extract of A. actinomycetemcomitans Y4. This material was found to react with rabbit polyclonal antiserum to serotype b but not with antisera specific for other A. actinomycetemcomitans serotypes. Analyses revealed that the O polysaccharide of Y4 LPS consists of a polymer of trisaccharide repeating units composed of D-Fuc, AL-Rha, and D-GalNAc residues. An identical structure was obtained for the O polysaccharide of LPS from A. actinomycetemcomitans JP2, another serotype b strain. These results indicate that the serotype b antigen of A. actinomycetemcomitans is defined by a trisaccharide repeating unit present in the O polysaccharide of LPS.

Lipopolysaccharide, LPS, structure, characterization, serotype, O-polysaccharide, O polysaccharide, Actinobacillus, Actinobacillus actinomycetemcomitans

NCBI PubMed ID: 8606081
Journal NLM ID: 0246127
Publisher: American Society for Microbiology
Correspondence: orbwil36@ubvms.cc.buffalo.edu
Institutions: Institute for Biological Sciences, National Research Council, Ottawa, Ontario, Canada, Instutute of Oral Microbiology and General Immunology, University of Zurich, Zurich, Switzerland, Department of Oral Biology, State University of New York at Buffalo, Buffalo, New York
Methods: NMR-2D, NMR

The human oropharyngeal pathogen Aggregatibacter (Actinobacillus) actinomycetemcomitans synthesizes multiple adhesins, including the non-fimbrial, extracellular matrix protein adhesin A (EmaA). EmaA monomers trimerize to form antennae-like structures on the surface of the bacterium, which are required for collagen binding. Two forms of the protein have been identified, which are suggested to be linked with the type of O-polysaccharide (O-PS) of the LPS synthesized (Tang et al., 2007). This association was investigated by generating individual mutants for a rhamnose sugar biosynthetic enzyme (rmlC, TDP-4-keto-6-deoxy-D-glucose 3, 5-epimerase), the ABC sugar transport protein (wzt) and the O-antigen ligase (waaL). All three mutants produced reduced amounts O-PS and the EmaA monomers in these mutants displayed a change in the electrophoretic mobility and aggregation state, as observed in SDS-polyacrylamide gels. The modification of EmaA with O-PS sugars was suggested by lectin blots using the fucose-specific Lens culinaris agglutinin (LCA). Fucose is one of the glycan components of the serotype b O-PS. The rmlC mutant strain expressing the modified EmaA protein demonstrated reduced collagen adhesion using an in vitro rabbit heart valve model, suggesting a role for the glycoconjugant in collagen binding. The data provide experimental evidence for the glycosylation of an oligomeric, coiled-coil adhesin, and for the dependence of the posttranslational modification of EmaA on the LPS biosynthetic machinery in A. actinomycetemcomitans.

O-polysaccharide, glycosylation, adhesin, Aggregatibacter actinomycetemcomitans, collagen adhesin EmaA

NCBI PubMed ID: 20061477
Journal NLM ID: 2985120R
Publisher: American Society for Microbiology
Correspondence: Keith.Mintz@uvm.edu
Institutions: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT, USA
Methods: SDS-PAGE, genetic methods, lectin blotting

The O-polysaccharide (O-PS; O-antigen) of bacterial lipopolysaccharides is made up of repeating units of one or more sugar residues and displays remarkable structural diversity. Despite the structural variations, there are only three strategies for O-PS assembly. The ATP-binding cassette (ABC)-transporter-dependent mechanism of O-PS biosynthesis is widespread. The Escherichia coli O9a and Klebsiella pneumoniae O2a antigens provide prototypes, which are distinguished by the fine details that link glycan polymerization and chain termination at the cytoplasmic face of the inner membrane to its export via the ABC transporter. Here, we describe the current understanding of these processes. Since glycoconjugate assembly complexes that utilize an ABC transporter-dependent pathway are widespread among the bacterial kingdom, the models described here are expected to extend beyond O-PS biosynthesis systems

Lipopolysaccharide, O-polysaccharide, ATP-binding cassette transporter, Escherichia coli O9a, Klebsiella pneumoniae O2a

NCBI PubMed ID: 22475157
Publication DOI: 10.1016/j.carres.2012.02.027
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: C. Whitfield
Institutions: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

The lipopolysaccharide (LPS) is the major constituent of the outer leaflet of the outer membrane of Gram-negative bacteria. Its lipid A moiety is embedded in the membrane and serves as an anchor for the rest of the LPS molecule. The outermost repetitive glycan region of the LPS is linked to the lipid A through a core oligosaccharide (OS), and is designated as the O-specific polysaccharide (O-polysaccharide, OPS) or O-antigen. The O-antigen is the most variable portion of the LPS and provides serological specificity, which is used for bacterial serotyping. The OPS also provides protection to the microorganisms from host defenses such as complement mediated killing and phagocytosis, and is involved in interactions of bacteria with plants and bacteriophages. Studies of the OPSs ranging from the elucidation of their chemical structures and conformations to their biological and physico-chemical properties help improving classification schemes of Gram-negative bacteria. Furthermore, these studies contributed to a better understanding of the mechanisms of pathogenesis of infectious diseases, as well as provided information to develop novel vaccines and diagnostic reagents.

Lipopolysaccharide, synthesis, lipopolysaccharides, structure, Bacterial, host, O-antigen, O antigen, cell, O antigens, O-antigens, chemical, interaction, cells, PDF, chemical synthesis, biogenesis

Publication DOI: 10.1007/978-3-7091-0733-1_3
Publisher: Springer
Correspondence: knirel@ioc.ac.ru
Editors: Knirel YA, Valvano MA
Institutions: Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia