1ACJ shows the crystal structure of Torpedo californica acetylcholinesterase (TcAChE) complexed with tacrine.[1]
Tacrine is a reversible inhibitor of cholinesterase. It was the first FDA approved drug for the treatment of Alzheimer's disease.
is stacked between the aromatic rings of tryptophan 84 and phenylalanine 330 (W84 and F330).[2]