Fluorescence polarization studies of saccharide binding to Wheat germ agglutinin and lysozyme

N-acetyl-D-glucosamine causes only slight increases in the polarization of Wheat germ agglutinin fluorescence at saturating levels whereas the disaccharide and trisaccharide produce increases in the polarization value from 0.116 to 0.151 and 0.154 respectively. These increases suggest that rotational motions of the tryptophan residue at the binding sites are being restricted by an interaction between these tryptophans and the bound sugars. A model of the nature and location of these interactions is discussed.Comparable results are obtained with lysozyme, which shows a larger effect upon binding of N-acetyl-D-glucosamine, but a maximal increase in polarization upon binding the corresponding disaccharide or trisaccharide.