Torpedo (a ray) AChE was used as the AChe model to interact with a ligand called tacrine.The following observations and findings were made by Sussman et al: In a complex with edrophonium the quaternary nitrogen of the ligand interacts with the indole of Trp-84 and its m-hydroxyl displays bifurcated hydrogen bonding to two members of the catalytic triad Ser200 and His440. In a complex with tacrine, the acridine is stacked against the indole of Trp84. The structural and chemical data together show the important role of aromatic groups as binding sites for quaternary ligand and they provide complementary evidence assigning Trp84 and Phe330 to the anionic subsite of the active site and Trp279 to the peripheral anionic site.
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AChE with Marked Residues
The model shows the AChE molecule and the residues, all shown as ribbons, Trp84, Ser200, His440, Trp279, and Phe330 in red. The ligand tacrine is show in a spacefilled model.
Trp84 Interaction with Tacrine
The indole of the residue Trp84 is clearly seen interacting with the tacrine molecule. This site is the anionic subsite of the AChE molecule, and choline recognition.
Ser200 and His440 Interaction with Tacrine
The Ser200 and the His440 molecule interact with the tacrine ligand. This interaction is in the from of hydrogen bonding. This site is the catalytic site of the AChE molecule.
Trp279 Interaction with Tacrine
Trp279 is the peripheral anionic site of the AChE molecule.
Phe330 Interaction with Tacrine
Phe330 is the anionic subsite of the AChE molecule.
All, amino acids in wireframe representation.
All, amino acids in spacefill representation.