Flexibility of active-site gorge aromatic residues and non-gorge aromatic residues in acetylcholinesterase

The presence of an unusually large number of aromatic residues in the active site gorge of acetylcholinesterase is a subject of great interest. Flexibility of these residues has been suspected to be a key player in controlling the ligand traversal in the gorge. This raises the question of whether the over-representation of aromatic residues in the gorge implies higher-than-normal flexibility of these residues. The current study suggests that it does not. Large changes in the hydrophobic cross-sectional area due to dihedral oscillations are probably the reason of their presence in the gorge.