The Interaction of Elderberry (Sambucus sieboldiana) Bark Lectin and Sialyloligosaccharides as Detected by1H-NMR1

摘要

The interaction of Japanese elderberry bark lectin (Sambucus sieboldianaagglutinin, SSA) with carbohydrate was investigated by1H-NMR. When a low affinity ligand, methylβ-D-galactoside (βMeGal), was mixed with SSA, each proton signal ofβMeGel was broadened. The signal of H-4 was markedly broad, while those of H-1, OCH3, and H-2 ofβMeGal were rather sharp. The specific broadening of Gal H-4 was more evident when SSA was mixed with methyl-β-D-lactoside (βMeLac). Position-dependent signal broadening suggests thatβMeGal binds to SSA such that H-4 is closely involved in the contact region, but H-1, OCH3, and H-2 are far from this region. In the case of a high affinity ligand, Neu5Ac(α2-6)Gal(β1-4)Glc(=N6L), ligand signals of the SSA-N6L mixture did not change at all. But when a small amount of N6L was added to the SSA-βMeGal mixture, the broad signals of boundβMeGal became dramatically sharp. This indicates that the added N6L molecules liberated the boundβMeGal from SSA. On the other hand, the sialyllactose with theα(2-3)-linkage(=N3L) could not substitute for boundβMeGal because of its lower affinity. This demonstrates that the competitive binding experiment between two ligands is a useful technique to detect the interaction of lectins with high affinity ligands which could not be observed directly by NMR signal broadening and/or chemical