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Studies on the carbohydrate moiety of Pla l 1 allergen. Identification of a major N‐glycan and significance for the immunoglobulin E‐binding activity
Author(s) -
Calabozo B.,
Barber D.,
Polo F.
Publication year - 2002
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1046/j.1365-2222.2002.01530.x
Subject(s) - glycan , fucose , glycoprotein , biochemistry , glycosylation , chemistry , immunoglobulin e , fucosylation , antibody , incubation , oligosaccharide , pngase f , allergen , microbiology and biotechnology , biology , immunology , allergy
Summary Background Pla l 1, the major allergen of Plantago lanceolata pollen, is a glycoprotein that contains an N‐glycosylation site. Carbohydrate moieties of many allergenic glycoproteins have been reported to be IgE‐binding determinants responsible for cross‐reactivity among different species. Objective To identify the kind of linkages and the type of glycans present in Pla l 1 and to investigate their contribution to the allergic response to this allergen. Methods Pla l 1 was deglycosylated by N‐glycosidase A and the IgE‐binding ability of the unglycosylated protein was evaluated by dot‐blot. Identification of β1 → 2 xylose and/or α1 → 3 fucose residues in Pla l 1 N‐glycan was carried out by incubation with specific antibodies from rabbit antiserum against HRP (anti‐HRP). The contribution of this N‐glycan to total IgE reactivity was analysed quantitatively by pre‐incubation of Pla l 1 with anti‐HRP prior to incubation with sera. The role of the carbohydrate moiety of Pla l 1 in cross‐reactivity was studied by RAST using unrelated glycoproteins with known sugar composition and structure. Results The effectiveness of N‐glycosidase A to deglycosylate Pla l 1 and the ineffectiveness of the treatment with PNGase F indicate that Pla l 1 carries a complex N‐glycan with an α1 → 3 fucose residue in its structure. Furthermore, the presence of β1 → 2 xylose and/or α1 → 3 fucose residues was identified in this N‐glycan by means of an ELISA. Pre‐incubation of Pla l 1 with an anti‐HRP antibody caused a weak but significant reduction in IgE reactivity. Some sera from P. lanceolata ‐allergic patients reacted positively with four glycoproteins that bear N‐glycans of complex type but not with fetuine. Conclusions Pla l 1 is a glycoprotein that carries at least a complex, major N‐linked glycan, with a α1 → 3 fucose residue in its structure and probably also a β1 → 2 xylose. This glycan moiety does not seem to constitute a relevant allergenic epitope of Pla l 1.