THERMODYNAMIC PARAMETERS OF THE INTERACTION OF URTICA-DIOICA AGGLUTININ WITH N-ACETYLGLUCOSAMINE AND ITS OLIGOMERS

The interaction between Urtica dioica agglutinin (UDA) and N-acetylglu cosamine (GlcNAc) and its beta(1-4)-linked oligomers was studied by fl uorescence titration and isothermal titration microcalorimetry. UDA po ssesses one significant binding site that can be measured calorimetric ally. This site is composed of three subsites, each subsite accommodat ing one GlcNAc residue. The interaction is enthalpically driven, and t he binding area of UDA is characterized by a Delta H of interaction fo r a given oligosaccharide considerably smaller than that of wheat germ agglutinin (WGA), despite the fact that they both belong to a family of proteins composed entirely of hevein domains. Relatively high Delta C-p values of the UDA-carbohydrate interactions and more favorable en tropy term compared to WGA suggest that binding of the carbohydrate li gands by UDA has a higher hydrophobic component than that of WGA.