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The presence and the level of antibodies in human sera against bacterial glycans are indications of prior encounters with similar antigens and/or the bacteria that express them by the immune system. An increasing number of pathogenic bacteria that cause human diseases have been shown to express polysaccharides containing a bacterial nonulosonic acid called 5,7-di--acetyllegionaminic acid (Leg5,7Ac). To investigate the immune recognition of Leg5,7Ac, which is critical for the fight against bacterial infections, a highly effective chemoenzymatic synthon strategy was applied to construct a library of α2-3/6-linked Leg5,7Ac-glycans via their diazido-derivatives (Leg5,7diN-glycans) formed by efficient one-pot three-enzyme (OP3E) synthetic systems from a diazido-derivative of a six-carbon monosaccharide precursor.

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Several bacterial flagellins are O-glycosylated with nonulosonic acids on surface-exposed Serine/Threonine residues by Maf glycosyltransferases. The Clostridium botulinum Maf glycosyltransferase (CbMaf) displays considerable donor substrate promiscuity, enabling flagellin O-glycosylation with N-acetyl neuraminic acid (Neu5Ac) and 3-deoxy-D-manno-octulosonic acid in the absence of the native nonulosonic acid, a legionaminic acid derivative. Here, we have explored the sequence/structure attributes of the acceptor substrate, flagellin, required by CbMaf glycosyltransferase for glycosylation with Neu5Ac and KDO, by co-expressing C.

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K63 capsular polysaccharide produced by Acinetobacter baumannii isolate LUH5551 (previously designated isolate O24) was re-examined using sugar analysis, Smith degradation, and one- and two-dimensional H and C NMR spectroscopy. Though previously reported as O24 consisting of linear tetrasaccharide units that include a 7-acetamido-5-acylamino form of 8-epilegionaminic acid [8eLeg5R7Ac, acylated at C5 with (S)-3-hydroxybutanoyl or acetyl (1:1)], the elucidated structure of the K63 type capsule was found to include a derivative of 5,7-diamino-3,5,7,9-tetradeoxy-d-glycero-d-galacto-non-2-ulosonic (legionaminic) acid, Leg5Ac7R, where R is either (S)-3-hydroxybutanoyl or an acetyl group (∼1:1 ratio). This finding is consistent with the presence of the lgaABCHIFG gene module for Leg5Ac7R biosynthesis in the KL63 gene cluster at the capsular polysaccharide (CPS) biosynthesis K locus in the LUH5551 genome.

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Enabling Chemoenzymatic Strategies and Enzymes for Synthesizing Sialyl Glycans and Sialyl Glycoconjugates.

Acc Chem Res

January 2024

Department of Chemistry, University of California, Davis, California 95616, United States.

Sialic acids are fascinating negatively charged nine-carbon monosaccharides. Sialic acid-containing glycans and glycoconjugates are structurally diverse, functionally important, and synthetically challenging molecules. We have developed highly efficient chemoenzymatic strategies that combine the power of chemical synthesis and enzyme catalysis to make sialic acids, sialyl glycans, sialyl glycoconjugates, and their derivatives more accessible, enabling the efforts to explore their functions and applications.

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Sporulation conditions influence the surface and adhesion properties of spores.

Front Microbiol

September 2023

Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, Lille, France.

Spore-forming bacteria of the group are responsible for recurrent contamination of processing lines in the food industry which can lead to food spoilage. The persistence of would be due to the high resistance of spores to extreme environmental condition and their propensity to contaminate surfaces. While it is well known that sporulation conditions modulate spore resistance properties, little is known about their effect on surface and adhesion properties.

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