Structural basis for defects of Keap1 activity provoked by its point mutations in lung cancer

Nrf2 regulates the cellular oxidative stress response, whereas Keapl represses Nrf2 through its molecular interaction. To elucidate the molecular mechanism of the Keapl and Nrf2 interaction, we resolved the six-bladed beta propeller crystal structure of the Kelch/DGR and CTR domains of mouse Keap1 and revealed that extensive inter- and intrablacle hydrogen bonds maintain the structural integrity and proper association of Keapl with Nrf2. A peptide containing the ETGE motif of Nrf2 binds the beta propeller of Keap1 at the entrance of the central cavity on the bottom side via electrostatic interactions with conserved arginine residues. We found a somatic mutation and a gene variation in human lung cancer cells that change glycine to cysteine in the DGR domain, introducing local conformational changes that reduce Keap1's affinity for Nrf2. These results provide a structural basis for the loss of Keapl function and gain of Nrf2 function.