Fig. 7.

(A) Modification hypothesis of CAPS. Positions, which can tolerate nonpolar/polar substituents, are shown as yellow/green spheres, respectively. (B) Polar (green) and neutral (yellow) water molecules at ligand coordinate providing clues about possible ligand modification. (C) Positions permitting polar substitutions. These modifications will be stabilized by the surrounding polar amino acids. (D) Small nonpolar substitutions such as halogens supported by hydrophobic amino acid residues. (E) van der Waals substitutions supported by hydrophobic amino acid residues.