Fig. 5. Hydrogen bonding involving the crystallographic water and His164 local environment. In each image, the NE nitrogen in the His164 side chain is colored magenta. (A) HD41-HE164 illustrating hydrogen bond donation from His164 to Thr175. (B) HD41-HD164 illustrating the His164 side chain rotation such that a hydrogen bond is formed with the backbone carbonyl of Met162. (C) HE41-HE164 illustrating the disruption of the hydrogen bonding interactions and loss of the interaction of the water with Asp187.