Mirror-image screening using d-proteins is a powerful approach to provide mirror-image structures of chiral natural products for drug screening. During the course of our screening study for novel MDM2-p53 interaction inhibitors, we identified that NPD6878 (R-(-)-apomorphine) inhibited both the native l-MDM2-l-p53 interaction and the mirror-image d-MDM2-d-p53 interaction at equipotent doses. In addition, both enantiomers of apomorphine showed potent inhibitory activity against the native MDM2-p53 interaction. In this study, we investigated the inhibitory mechanism of both enantiomers of apomorphine against the MDM2-p53 interaction. Achiral oxoapomorphine, which was converted from chiral apomorphines under aerobic conditions, served as the reactive species to form a covalent bond at Cys77 of MDM2, leading to the inhibitory effect against the binding to p53.
Keywords: Apomorphine; MDM2; Michael acceptor; Mirror-image screening; Oxoapomorphine; p53.
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