Molecular modeling and crystal structure of ERK2–hypothemycin complexes

Resorcylic acid lactones containing a cis-enone—such as hypothemycin—are susceptible to Michael addition reactions and are potent and specific inhibitors of about 45 of the known Ser/Thr/Tyr protein kinases. These inhibitors bind reversibly, and then form a covalent adduct with a completely conserved cysteine in the ATP binding site of their target kinases. As a paradigm for the structures of the cis-enone resorcylic acid lactone complexes with this subset of kinases, we have modeled the structure of ERK2–hypothemycin reversible and covalent complexes using docking and extended molecular dynamics simulations. Subsequently, we determined the 2.5 Å resolution crystal structure of the complex that was in excellent accord with the modeled structure. The results were used to discuss structure–activity relationships, and provide a structural template for the development of irreversible inhibitors that complement the ATP binding site of kinases.