The Conformation of the T-antigen Disaccharide Bound toMaclura pomiferaAgglutinin in Aqueous Solution

Thomas Weimar, Ralph Bukowski, N. Martin Young
2000 Journal of Biological Chemistry  
The complex of Maclura pomifera agglutinin with the T-antigen disaccharide (␤-D-Gal-(133)-␣-D-GalNAc-(13O)-Me) was investigated by NMR spectroscopy in aqueous solution. Intramolecular transferred nuclear Overhauser enhancement (NOE) effects between the monosaccharide moieties were used to derive the ligand conformation in the lectin-bound state. Ligand protons in contact with the protein were identified by saturation transfer difference experiments and intermolecular transferred NOE effects. It
more » ... red NOE effects. It is demonstrated that structural differences exist for the ligand-lectin complex in aqueous solution as compared with the previously published crystal structure (Lee, X., Thompson, A., Zhiming, Z., Ton-that, H., Biesterfeldt, J., Ogata, C., Xu, L., Johnston, R. A. Z., and Young, N. M. (1998) J. Biol. Chem. 273, 6312-6318). In order to accommodate the O-methyl group of the disaccharide, the amino acid side chain of Tyr-122 has to rotate from its position in the crystal. The NMR data are in accord with two conformational families at the ␤-(133)glycosidic linkage in the solution complex with interglycosidic angles / ‫؍‬ 45/؊65°and ؊65/ ؊18°. These differ from the bound conformation of the ligand in the crystal (/ ‫؍‬ 39/؊8°) and are not highly populated by the ligand in the free state. The reason for the structural differences at the ␤-(133)glycosidic linkage are hydrogen bonds that stabilize the relative orientation of the monosaccharide units in the crystal. Our results demonstrate that the crystallization of a protein-carbohydrate complex can interfere with the delicate process of carbohydrate recognition in solution.
doi:10.1074/jbc.m005092200 pmid:10913148 fatcat:egbkuuo2bng5zir6rgvdr5po4m