MOLECULAR MODELING OF THE DOLICHOS-BIFLORUS SEED LECTIN AND ITS SPECIFIC INTERACTIONS WITH CARBOHYDRATES - ALPHA-D-N-ACETYL-GALACTOSAMINE, FORSSMAN DISACCHARIDE AND BLOOD-GROUP-A TRISACCHARIDE

The three-dimensional structure of Dolichos biflorus seed lectin has b een constructed using five legume lectins for which high resolution cr ystal structures were available. The validity of the resulting model h as been thoroughly investigated. Final structure optimization was cond ucted for the lectin complexed with alpha GalNAc, providing thereby th e first three-dimensional structure of lectin/GalNAc complex. The role of the N-acetyl group was clearly evidenced by the occurrence of a st rong hydrogen bond between the protein and the carbonyl oxygen of the carbohydrate and by hydrophobic interaction between the methyl group a nd aromatic amino acids. Since the lectin specificity is maximum for t he Forssman disaccharide alpha GalNAc(1-3)beta GalNAc-O-Me and the blo od group A trisaccharide alpha GalNAc(1-3)alpha Fuc(1-2)beta Gal-O-Me, the complexes with these oligosaccharides have been also modelled.