FIGURE 5.

Pharmacophores for L and B binding sites. The residues and functional groups on the protein that interact critically with the chitobiose are shown. The average distance between the functional groups on the protein is given; the average deviation is 0.25 Å for the loop site and 0.15 Å for the barrel site. a, three-dimensional pharmacophore for loop binding site. Three interactions define a plane for the chitobiose unit. The two-dimensional pharmacophore is shown in c. All three residues interact with chitobiose through hydrogen bonds. b, projection of three-dimensional pharmacophore for the barrel binding site. The two-dimensional pharmacophore is shown in d. Trp-103, Thr-145, and Thr-153 define a plane for the chitobiose unit, whereas Asp-159 and Asp-117 are out of the plane, in a boat configuration. Thr-145, Thr-153, and Asp-159 all interact with the chitobiose through hydrogen bonds, Asp-117 through electrostatic interactions while an alcohol on chitobiose interacts with the aromatic ring of Trp-103.