Fig. 9. Ketoamide hydrogen bonding in the HE41-HD164 protonation state. In both panels, hydrogen bonds between the ligand (light green licorice) and the protein are indicated with a blue line, while those with water or between protein residues are red. (A) Region around the crystallographic water. (B) conformation in which the His164 has rotated, making a hydrogen bond with the backbone of Met162. The loss of the interaction with Asp187, which is present in the crystal structures, is illustrated.
