An inhibited conformation for the protein kinase domain of the Saccharomyces cerevisiae AMPK homolog Snf1

AMP-activated protein kinase (AMPK) is a master metabolic regulator for controlling cellular energy homeostasis. Its homolog in yeast, SNF1, is activated in response to glucose depletion and other stresses. The catalytic (alpha) subunit of AMPK/SNF1 in yeast (Snf1) contains a protein Ser/Thr kinase domain (KD), an auto-inhibitory domain (AID) and a region that mediates interactions with the two regulatory (beta and gamma) subunits. Here, the crystal structure of residues 41-440 of Snf1, which include the KD and AID, is reported at 2.4 A resolution. The AID is completely disordered in the crystal. A new inhibited conformation of the KD is observed in a DFG-out conformation and with the glycine-rich loop adopting a structure that blocks ATP binding to the active site.