Synthesis of the antigenic tetrasaccharide side chain from the major glycoprotein of Bacillus anthracis exosporium.
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ABSTRACT:
SUBMITTER: Crich D
PROVIDER: S-EPMC2615471 | biostudies-literature | 2007 Aug
REPOSITORIES: biostudies-literature
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Synthesis of the antigenic tetrasaccharide side chain from the major glycoprotein of Bacillus anthracis exosporium.
Crich David D Vinogradova Olga O
The Journal of organic chemistry 20070728 17
A synthesis of the pentenyl glycoside of the tetrasaccharide side chain from the major glycoprotein of Bacillus anthracis by a [3 + 1] approach is described. The construction of the 1,2-trans-glycosidic linkage in the terminal anthrose moiety was achieved through the application of known alpha-nitrilium ion-mediated beta-selective glycosylation methodology. An iterative glycosylation strategy was used for the assembly of the trirhamnan building block. A new route to the anthrose saccharide was d ...[more]
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Project description:The tetrasaccharide (2-O-methyl-4-(3-hydroxy-3-methylbutamido)-4,6-dideoxy-?-d-glucopyranosyl-(1?3)-?-l-rhamnopyranosyl-(1?3)-?-l-rhamnopyranosyl-(1?2)-l-rhamnopyranose) from the major exosporium protein (BclA) of Bacillus anthracis has been proposed as a target for development of diagnostics and immune therapy or prophylaxis. While the immunodominant character of the anthrose residue has been previously elucidated, the role of the stereochemical configuration of the downstream rhamnose is unknown. Because the linkage of this residue to the GlcNAc bridging the glycan and the protein is lost during isolation of the tetrasaccharide, its ?- and ?-glycoforms have been synthesized. Herein, we prepared neoglycoconjugates from a series of fragments of the tetrasaccharide, including the complete ?- and ?-tetrasaccharide glycoforms, a 2-demethoxylated version of the ?-tetrasaccharide, and the ?- and ?-trirhamnosides and CRM197. By immunization of mice, we showed that the anti ?- and ?-tetrasaccharide serum equally recognized both glycoforms. In contrast the sera produced following immunization with the ?- and ?-trirhamnoside fragments exhibited higher recognition for their own antigens than for their anomeric counterparts. The anti ?- and ?-tetrasaccharide sera recognized Sterne spores in a comparable fashion. ?BclA spores not expressing the major exosporium protein were also recognized by the same sera, while mutants that produced the carbohydrate antigen with deletion of either rhamnose or anthrose were not. The tetrasaccharide could, therefore, be expressed in proteins other than BlcA. This work proves that ?- and ?-tetrasaccharide are equally potent immunogens.
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Project description:The spores of the Bacillus cereus group (B. cereus, Bacillus anthracis, and Bacillus thuringiensis) are surrounded by a paracrystalline flexible yet resistant layer called exosporium that plays a major role in spore adhesion and virulence. The major constituent of its hairlike surface, the trimerized glycoprotein BclA, is attached to the basal layer through an N-terminal domain. It is then followed by a repetitive collagen-like neck bearing a globular head (C-terminal domain) that promotes glycoprotein trimerization. The collagen-like region of B. anthracis is known to be densely substituted by unusual O-glycans that may be used for developing species-specific diagnostics of B. anthracis spores and thus targeted therapeutic interventions. In the present study, we have explored the species and domain specificity of BclA glycosylation within the B. cereus group. First, we have established that the collagen-like regions of both B. anthracis and B. cereus are similarly substituted by short O-glycans that bear the species-specific deoxyhexose residues anthrose and the newly observed cereose, respectively. Second we have discovered that the C-terminal globular domains of BclA from both species are substituted by polysaccharide-like O-linked glycans whose structures are also species-specific. The presence of large carbohydrate polymers covering the surface of Bacillus spores may have a profound impact on the way that spores regulate their interactions with biotic and abiotic surfaces and represents potential new diagnostic targets.
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2023-04-04 | GSE220794 | GEO
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