Mechanism-based design of a protein kinase inhibitor

Protein kinase inhibitors have applications as anticancer therapeutic agents and biological tools in cell signaling. Based on a phosphoryl transfer mechanism involving a dissociative transition state, a potent and selective bisubstrate inhibitor for the insulin receptor tyrosine kinase was synthesized by linking ATPγS to a peptide substrate analog via a two-carbon spacer. The compound was a high affinity competitive inhibitor against both nucleotide and peptide substrates and showed a slow off-rate. A crystal structure of this inhibitor bound to the tyrosine kinase domain of the insulin receptor confirmed the key design features inspired by a dissociative transition state, and revealed that the linker takes part in the octahedral coordination of an active site Mg²⁺. These studies suggest a general strategy for the development of selective protein kinase inhibitors.