A STRUCTURE OF THE COMPLEX BETWEEN CONCANAVALIN-A AND O-(ALPHA-D-MANNOPYRANOSYL)-ALPHA-D-MANNOPYRANOSIDE REVEALS 2 BINDING MODES

The structure of concanavalin A in complex with the trimannoside O-(al pha-D-mannopyranosyl)-alpha-D-mannopyranoside has been determined in a novel space group, In three of the four subunits of the concanavalin A tetramer, the interactions between the protein and the bound sacchar ide are essentially identical to those reported previously by other au thors (Naismith, J, H., and Field, R, A. (1996) J, Biol, Chem, 271, 97 2-976), In the fourth subunit, however, the alpha 1-->3 linkage has a different conformation, resulting in a different part of the alpha 1-- >3-linked mannose interacting with essentially the same surface of the protein, Furthermore, significant differences are observed in the qua ternary associations of the subunits compared with the saccharide-free structures and other carbohydrate complexes, suggesting that the conc anavalin A tetramer is a rather flexible entity.