Small molecule inhibitors of IκB kinase β: A chip-based screening and molecular docking simulation

초록

A chip-based screening system for I kappa B kinase beta (IKK beta) has been developed by physically immobilizing the substrate I beta B alpha on a glass matrix using a calixarene linker. Phosphorylation of I beta B alpha by IKK beta and ATP was quantitated using a fluorescently labeled antibody. Using this efficient assay system a chemical library of 2000 bioactive compounds was screened against IKK beta and four were identified as good inhibitors, namely, aurintricarboxylic acid, diosmin, ellagic acid, and hematein. None of them have been reported to be an inhibitor of IKK beta although they were implicated in various NF kappa B-mediated biological processes. Our enzyme-based assay showed that IC50 of the four inhibitors is comparable with that of IKK-16, a previously known strong inhibitor. Molecular docking simulation shows that the hydrophobic moiety of an inhibitor interacts with the four hydrophobic residues (Leu21, Val29, Val152, and Ile165) of the active site. The MM-PBSA calculation suggests that these hydrophobic interactions appear to be the predominant contributor to the binding free energy. As IKK beta is ubiquitously expressed in various cell types and executes many biological functions, the enzyme and cell specificity of the four inhibitors need to be rigorously tested before accepted as a drug candidate.

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