Crystallization and structure of ebselen bound to cysteine 141 of human inositol monophosphatase (IMPase)

Inositol monophosphatase (IMPase) is inhibited by lithium, the most efficacious treatment for bipolar disorder. Several therapies have been approved, or are going through clinical trials, aimed at the replacement of lithium in the treatment of bipolar disorder. One candidate small molecule is ebselen, a selenium-containing antioxidant, which has been demonstrated to produce lithium-like effects, both in a murine model and in clinical trials. Here we present the crystallization and first structure of human IMPase covalently complexed with ebselen, a 1.47[A] crystal structure (PDB entry 6ZK0). In the human-IMPase-complex ebselen, in a ring opened conformation, is covalently attached to Cys141, a residue located away from the active site. IMPase is a dimeric enzyme and, in the crystal structure, two adjacent dimers share four ebselen molecules, creating a tetramer with ~222 symmetry. In the crystal structure presented in this publication, the active site in the tetramer is still accessible, suggesting that ebselen may function as an allosteric inhibitor, or may block the binding of partner proteins. SynopsisHere we present a 1.47[A] crystal structure of human inositol monophosphatase (IMPase) bound to the inhibitor ebselen. In the structure, ebselen forms a seleno-sulfide bond with cysteine 141 and ebselen-mediated contacts between two dimers give a ~222 tetramer.