Figure 4. Choline can selectively bind to the closed protein conformation S1 to reach the holo state.

(a) The X-ray bound conformation (red, PDB ID: 2REG) is superimposed with a conformation selected from MD simulations in the presence of ligands and with smallest RMSD to the bound state (blue). Four critical residues in the binding sites that are in direct contact with the ligand are highlighted in stick representation. (b) Distances (Å) between the center of mass of ligand and four centers of mass of critical residues in the binding site obtained from the holo structure (red bars) and five MD trajectories in which only those conformations after the ligand binding have been included in the analysis (blue bars).