The active site of monomer-B of Homoc-DADMe-ImmA-SeMTAN. The figure shows the hydrogen bonds (red dotted lines) between a bound inhibitor (homocysteine-DADMe-ImmA) and SeMTAN. A short water trail with the associated hydrogen bonding network is included. Tyr107 is part of the neighboring monomer-A. Waters are shown as red spheres and W1-W4 waters are discussed in the text. W1 is the catalytic water molecule. The carbons, oxygens, nitrogens and sulfurs are colored in grey, red, blue and yellow, respectively. The hydrogen bonding distances are shown in angstroms (Å). The figure was prepared with PyMOL.