Figure 2. (A) The RMSD traces of the protonated Glu202. (B) The RMSD traces of the deprotonated Glu202. (C) The representative structure of the key hydrogen bond network with Glu202 being protonated in comparison to that in the crystal structure. (D) The representative structure of the key hydrogen bond network with Glu202 being deprotonated in comparison to that in the crystal structure. The carbon atoms in the crystal structure are colored with green, and the carbon atoms in the Glu202-protonated and Glu202-deprotonated structures are colored with orange and light blue, respectively. The oxygen, nitrogen, and hydrogen atoms are colored red, blue, and white, respectively. The key water molecules are rendered as ball and stick. The black dashed lines are the simulated hydrogen bonds associate with the key water molecule. The distances of the hydrogen bonds are labeled with yellow background and are in the angstrom unit. All nonpolar hydrogen atoms are not shown for clarity.