Activation of AMP-Activated Protein Kinase Revealed by Hydrogen/Deuterium Exchange Mass Spectrometry

AMP-activated protein kinase (AMPK) monitors cellular energy, regulates genes involved in ATP synthesis and consumption, and is allosterically activated by nucleotides and synthetic ligands. Analysis of the intact enzyme with hydrogen/deuterium exchange mass spectrometry reveals conformational perturbations of AMPK in response to binding of nucleotides, cyclodextrin, and a synthetic small molecule activator, A769662. Results from this analysis clearly show that binding of AMP leads to conformational changes primarily in the gamma subunit of AMPK and subtle changes in the alpha and beta subunits. In contrast, A769662 causes profound conformational changes in the glycogen binding module of the 13 subunit and in the kinase domain of the a subunit, suggesting that the molecular binding site of the latter resides between the a and beta subunits. The distinct short- and long-range perturbations induced upon binding of AMP and A769662 suggest fundamentally different molecular mechanisms for activation of AMPK by these two ligands.