Image

Natalie Ahn, University of Colorado, Boulder

Title: "Allosteric Communication and Conformational Selection in the MAP kinase, ERK2"

Abstract:

Activation of the extracellular signal regulated kinase 2 (ERK2) by phosphorylation is accompanied by changes in protein motions, as determined by hydrogen-deuterium exchange mass spectrometry (HDX-MS) and NMR relaxation dispersion measurements. These can be described as a global exchange between two conformational states that are associated with movements needed to form productive interactions with nucleotide. Small molecule inhibitors of ERK1/2 exploit the low energetic difference between these states, shifting the equilibrium to allow conformational selection in binding. They reveal coupling between motions in the activation loop and those surrounding the catalytic site in the active form of the kinase. Molecular dynamics simulations of 2P-ERK2 exhibit multiple conformations of the activation loop that deviate from the starting X-ray structure (PDB:2ERK) with variability in salt bridges formed between pY185 and the kinase core. Analyses of these conformers suggest a pathway that couples the activation loop to residues within the active site, connected through the C-terminal L16 segment. These findings, together with the variability in conformation selection among a panel of ATP-competitive ERK1/2 inhibitors, yield insight into the nature of the conformational exchange and how it enables kinase activation. In this way, ERK2 serves as a useful prototype to investigate the importance of protein dynamics for kinase regulation and inhibitor action.