The monosaccharide binding site of lentil lectin: an X-ray and molecular modelling study.

The X-ray crystal structure of lentil lectin in complex with α-d-glucopyranose has been determined by molecular replacement and refined to anR-value of 0.20 at 3.0 A resolution. The glucose interacts with the protein in a manner similar to that found in the mannose complexes of concanavalin A, pea lectin and isolectin I fromLathyrus ochrus. The complex is stabilized by a network of hydrogen bonds involving the carbohydrate oxygens O6, O4, O3 and O5. In addition, the α-d-glucopyranose residue makes van der Waals contacts with the protein, involving the phenyl ring of Phe123β. The overall structure of lentil lectin, at this resolution, does not differ significantly from the highly refined structures of the uncomplexed lectin.