[摘要]：Previously, the authors designed and synthesized a potent NF-kB inhibitor, DHMEQ. Although DHMEQ showed potent anti-inflammatory and anticancer activities in animals, its mol. target has not been elucidated. In the present study, its target protein was found to be p65 and other Rel homol. proteins. The authors found that (-)-DHMEQ bound to p65 covalently with a 1:1 stoichiometry by conducting SPR and MALDI-TOF MS analyses. MS anal. of the chymotrypsin-digested peptide suggested the binding of (-)-DHMEQ to a Cys residue. Formation of Cys/(-)-DHMEQ adduct in the protein was supported by chem. synthesis of the adduct. Substitution of specific Cys in p65 and other Rel homol. proteins resulted in the loss of (-)-DHMEQ binding. (-)-DHMEQ is the first NF-kB inhibitor that was proven to bind to the specific Cys by chem. methodol. These findings may explain the highly selective inhibition of NF-kB and the low toxic effect of (-)-DHMEQ in cells and animals.
