Structural identification of vasodilator binding sites on the SUR2 subunit.

ATP-sensitive potassium channels (K ATP ), composed of Kir6 and SUR subunits, convert the metabolic status of the cell into electrical signals. Pharmacological activation of SUR2- containing K ATP channels by class of small molecule drugs known as K ATP openers leads to hyperpolarization of excitable cells and to vasodilation. Thus, K ATP openers could be used to treat cardiovascular diseases. However, where these vasodilators bind to K ATP and how they activate the channel remains elusive. Here, we present cryo-EM structures of SUR2A and SUR2B subunits in complex with Mg-nucleotides and P1075 or levcromakalim, two chemically distinct K ATP openers that are specific to SUR2. Both P1075 and levcromakalim bind to a common site in the transmembrane domain (TMD) of the SUR2 subunit, which is between TMD1 and TMD2 and is embraced by TM10, TM11, TM12, TM14, and TM17. These K ATP openers synergize with Mg-nucleotides to stabilize SUR2 in the NBD-dimerized occluded state to activate the channel.