The binding of fucose-containing glycoproteins by hepatic lectins. The binding specificity of the rat liver fucose lectin.

摘要: The parameters that affect the interaction of ligands with a fucose-binding lectin from rat liver have been examined. 125I-Fucosyl-bovine serum albumin (Fuc-BSA) containing 50 residues fucose/molecule was used as standard ligand. At low initial concentrations ligand (10 ng/ml) and (140 ng/ml), reaction reaches equilibrium at pH 7.8, 23 degrees C, within 40 min. binding is Ca2+ dependent half-maximal occurring 54 microM Ca2+; several metal ions tested, only Sr2+ partially replaced Ca2+. Binding maximal between 7.6 8.6, fell slightly up to 10, but markedly below 7. lectin-ligand complexes dissociated pH, on removal Ca2+, or in presence large excess competing apparent association constant (Ka) for Fuc-BSA 1.75 X 10(8) M-1. fucose content also influenced binding, little 24 residues/molecule residues/molecule. With knowledge influencing sensitive reproducible assays were developed. specificity examined by measuring inhibition 125I-Fuc-BSA neoglycoproteins, monosaccharides, glycosides direct neoglycoproteins. Galactosides beta-linked fucosides best among much weaker mannosyl- N-acetylglucosaminyl-BSA. On basis pattern various monosaccharides glycosides, it possible propose conformations saccharides fit lectin-binding site. C1 conformation N-acetyl-D-galactosamine fits best, although other not obviously related such L-fucose, L-arabinose, D-mannose can assume permit them be effective inhibitors. neoglycoproteins differs pure hepatic lectins. Thus, has high affinity galactosyl-BSA galactose binds shows either N-acetylglucosaminyl-BSA Fuc-BSA. In contrast, mannose/N-acetylglucosamine galactosyl-BSA.