Structural Studies of ERK2 Protein Complexes.

ERK1 and ERK2 (ERK1/2) are the primary effector kinases of the RAS-RAF-MEK-ERK signaling pathway. A variety of substrates and regulatory partners associate with ERK1/2 through distinct D-peptide- and DEF-docking sites on their kinase domains. While understanding of D-peptides that bind to ERK1/2 has become increasingly clear over the last decade, only more recently have structures of proteins interacting with other binding sites on ERK1/2 become available. PEA-15 is a 130-residue ERK1/2 regulator that engages both the D-peptide- and DEF-docking sites of ERK kinases, and directly sequesters the ERK2 activation loop in various different phosphorylation states. Here we describe the methods used to derive crystallization-grade complexes of ERK2-PEA-15, which may also be adapted for other regulators that associate with the activation loop of ERK1/2.