Co-crystallization of human inositol monophosphatase with the lithium mimetic L-690,330

Abstract

Lithium, which is still the gold standard in the treatment of bipolar disorder, has been proposed to inhibit inositol monophosphatase (IMPase) and is hypothesized to exert its therapeutic effects by attenuating phosphatidylinositol (PI) cell signalling. Drug‐discovery efforts have focused on small‐molecule lithium mimetics that would specifically inhibit IMPase without exhibiting the undesired side effects of lithium. L‐690,330 is a potent bisphosphonate substrate‐based inhibitor developed by Merck Sharp & Dohme. To aid future structure‐based inhibitor design, determination of the exact binding mechanism of L‐690,330 to IMPase was of interest. Here, the high‐resolution X‐ray structure of human IMPase in complex with L690,330 and manganese ions determined at 1.39 Å resolution is reported.

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

“…Cys125 has no surface accessibility whether oxidised or reduced. A partial Cys25-Cys125 disulphide is also observed in 6GJ0 (Kraft et al, 2018).…”

“…The IMPase construct was described by Kraft et al 2018, with Rossetta2(DE3) E. coli used for IMPase production. A starter culture (10 ml) of transformed E. coli was grown overnight and used to inoculate 1L of LB medium containing 2.5 mM betaine, 660 mM sorbitol, 35 mg/ml chloramphenicol and 50 mg/ml ampicillin.…”

“…The structure was solved by rigid body refinement from the 1.7Å crystal structure of IMPase with Mn (PDB entry 6GJ0; Kraft et al, 2018). Initial structure solution used the DIMPLE pipeline; this pipeline provides the user with a quick method to identify datasets that have a bound ligand or drug candidate in their crystal (http://ccp4.github.io/dimple/; Wojdyr et al, 2013).…”

“…Each active site contains three Mn 2+ ions in 6GJ0 (Kraft et al, 2018), while in 2BJI (Gil et al, 2005) each active site contains three Mg 2+ ions. In our structure, site 2 (Gill et al, 2005) does not have enough electron density for a Mn 2+ ion (Mn 2+ ions have twenty-three electrons).…”

“…These multiple targets suggest that several potential therapeutic uses for ebselen, but also that there are likely to be off-target related side effects. (Kraft et al, 2018). In this paper we present a 1.47Å structure of ebselen covalently bound to cysteine residue 141 of human IMPase.…”