Fig 3. Classification of His524 conformations (PDB IDs: 2YJA, 4IVY, and 4IWC).

Closed (A) and moved back (B) conformations which stabilize protein-ligand complex through hydrogen bond and hydrophobic interaction, respectively. Open conformation (C) that provides an expanded binding pocket for ligands longer than 13 Å. Ligands are colored in orange with hydrogen, oxygen, nitrogen, sulfur, and fluorine atoms in white, red, blue, yellow, and green, respectively.