The Discovery of Direct Noncovalent Bonded Interaction between Keap1 and Diethyl Maleate through Molecular Dynamics Simulations

Abstract

Keap1 negatively regulates the function of Nrf2 that is a major activator of genes encoding phase 2 detoxifying enzymes via sequestering cytoplasmic Nrf2 and subsequent degradation through the proteasome system. Reactive cysteine residues of Keap1 could be modified by Michael reaction acceptor molecules. Previous studies have shown that adduction at Cys151 by diethyl maleate (DEM) can give rise to a significant conformational change in Keap1 that leads to the dissociation of Keap1 from CUL3, hence inhibits Nrf2 ubiquitylation. The BTB domain of Keap1 plays a crucial role in both forming self-dimerization and binding to CUL3. In order to better understanding the molecular mechanism how DEM interact with amino acid residues around Cys151, we performed two molecular dynamics (MD) simulations including Keap1-DEM complex and Keap1 alone (control group). Interestingly, we found that after a short period of lingering around Cys151, DEM ultimately stabilized in a gap between two specific helixes away from the cavity around Cys151 and induced a concomitant significant conformational change of BTB domain of Keap1. Similar phenomenon, however, was not observed in the control group. These results suggested that DEM could impair the normal function of Keap1 by inducing the conformational change of BTB domain via direct noncovalent bonded interaction. Our research provides a new insight into another way of interaction between Keap1 and DEM in spite of their known Michael addition reaction, by which novel phase2 enzyme inducer drugs with higher specificity could be discovered in the future