D166

Kinase Glossary: D166

D166 is a key conserved residue in ePK and most PKL kinases. It is known as the catalytic aspartate or catalytic base and is part of the catalytic loop motif HxDxxxxN. While the catalytic mechanism of protein kinases is not fully resolved, the side chain carboxyl group of D166 does hydrogen bond to the hydroxyl group of the substrate residue and facilitates phospho-transfer. It is one of three residues (along with K72 and D184) whose absence is used to predict pseudokinases. The number 166 is based on the position of this residue in the first PKA kinase crystal, 1ATP.