7mjq
Vascular KATP channel: Kir6.1 SUR2B quatrefoil-like conformation 2
Structural highlights
FunctionKCNJ8_RAT This potassium channel is controlled by G proteins. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. Can be blocked by external barium.[1] Publication Abstract from PubMedVascular tone is dependent on smooth muscle K(ATP) channels comprising pore-forming Kir6.1 and regulatory SUR2B subunits, in which mutations cause Cantu syndrome. Unique among K(ATP) isoforms, they lack spontaneous activity and require Mg-nucleotides for activation. Structural mechanisms underlying these properties are unknown. Here, we determined cryogenic electron microscopy structures of vascular K(ATP) channels bound to inhibitory ATP and glibenclamide, which differ informatively from similarly determined pancreatic K(ATP) channel isoform (Kir6.2/SUR1). Unlike SUR1, SUR2B subunits adopt distinct rotational "propeller" and "quatrefoil" geometries surrounding their Kir6.1 core. The glutamate/aspartate-rich linker connecting the two halves of the SUR-ABC core is observed in a quatrefoil-like conformation. Molecular dynamics simulations reveal MgADP-dependent dynamic tripartite interactions between this linker, SUR2B, and Kir6.1. The structures captured implicate a progression of intermediate states between MgADP-free inactivated, and MgADP-bound activated conformations wherein the glutamate/aspartate-rich linker participates as mobile autoinhibitory domain, suggesting a conformational pathway toward K(ATP) channel activation. Vascular K(ATP) channel structural dynamics reveal regulatory mechanism by Mg-nucleotides.,Sung MW, Yang Z, Driggers CM, Patton BL, Mostofian B, Russo JD, Zuckerman DM, Shyng SL Proc Natl Acad Sci U S A. 2021 Nov 2;118(44):e2109441118. doi: , 10.1073/pnas.2109441118. PMID:34711681[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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