Docking site peptide induced release of sequestered phosphorylation sites in the MAP kinase ERK2

Abstract

MAP kinases interact with substrates and processing enzymes at sites outside their active sites. D-domain docking site sequences have been identified and studied structurally in complex with p38a and JNK1. We have now carried out high resolution crystallographic analysis of unphosphorylated ERK2 bound to D-domain docking site peptides derived from MEK2, an activator, and hematopoietic tyrosine phosphatase, a negative regulator of ERK2. In the complexes, electrostatic interactions anticipated from mutagenic analysis between the basic region of the docking sites and the CD domain of ERK2 are observed for the first time. The ØA-X-ØB motif of pepHePTP makes interactions that different are from those observed in p38a and JNK1. Large conformational changes, especially in the activation loop of ERK2, accompany complex formation. Phosphorylation sites in the activation loop of ERK2, which are buried in low activity ERK2, become exposed to solution in the complex. We propose that the induced conformational changes in the activation loop serve to release the sequestered phosphorylation sites for processing. The conformational changes are unique in each subfamily. The allosteric feature probably contributes to pathway specificity of MAP kinases. This work was supported by funding from the NIH (DK46993 to EJG).