The (1 → 3)-linked α- l-fucosyl group of the N-glycans of the Wistaria floribunda lectins is recognized by a rabbit anti-serum

Abstract

An increasing number of plant glycoproteins have been shown to possess a characteristic N-glycan component containing a β-(1 → 2)-linked d-xylose unit on the core β- d-mannose unit, and an α-(1 → 3)-linked l-fucose unit on the asparagine-linked 2-acetamido-2-deoxy- d-glucose unit. Wistaria floribunda seeds have two distinct lectins; the erythroagglutinin, WFA, and the lymphocyte mitogen, WFM. Earlier studies indicated that both lectins belong to such a class of glycoproteins. We now report the complete structural analysis of Pronase glycopeptides derived from WFA. On the basis of chemical treatment of the glycopeptides, carbohydrates composition and methylation analysis of fluorescein-labeled glycopeptides, and their susceptibility to specific exoglycosidases, the structure of the WFA glycan was found to be, α- d-Man p-(1 → 6)-[β- d-Xyl p-(1 → 2)]-[α- d-Man p(1 → 3)]-β- d-Man p(1 → 4)-β- d-Glc pNAc-[α- l-Fuc p-(1 → 3)]-β- d-Glc p-NAc-(1 → N). Quantitative studies on the interaction of the original fluorescein-labeled glycopeptide and its specific degradation products with a rabbit anti-glycan antibody, developed against WFM, showed that the (1 → 3)-linked α- l-fucose unit is essential for interaction. Loss of the terminal α- d-mannosyl groups resulted in decreased, though detectable binding.