The carbohydrate-binding specificity of pea and lentil lectins. Fucose is an important determinant.
The carbohydrate-binding specificities of pea lectin and lentil lectin have been determined by testing the ability of radioactively labeled glycopeptides to bind to columns of pea lectin-Sepharose and lentil lectin-Sepharose. The presence of a fucose residue attached to the asparagine-linked N-acetylglucosamine residue of the test glycopeptide was essential for high affinity binding to both pea and lentil lectin-Sepharose but not to concanavalin A-Sepharose. In addition to fucose, 2 alpha-mannosyl residues were required for glycopeptide binding to the pea and lentil lectin-Sepharose columns. Substitution of the alpha-mannosyl residues at C-2 did not prevent their interaction. Substitution of 1 alpha-mannosyl residue at both C-2 and C-4 did prevent glycopeptide binding, but substitution of 1 alpha-mannosyl residue at C-2 and C-6 did not impair binding. Glycopeptide binding to lentil lectin-Sepharose was enhanced by the exposure of terminal N-acetylglucosamine residues on the glycopeptide, whereas binding to pea lectin-Sepharose was enhanced by the exposure of terminal mannose residues. The differences in carbohydrate binding specificity of pea lectin-Sepharose and Con A-Sepharose were exploited to fractionate a mixture of [2-3H]mannose-labeled glycopeptides derived from mouse lymphoma cell glycoproteins.