2gix
From Proteopedia
Cytoplasmic Domain Structure of Kir2.1 containing Andersen's Mutation R218Q and Rescue Mutation T309K
Structural highlights
Function[IRK2_MOUSE] Probably participates in establishing action potential waveform and excitability of neuronal and muscle tissues. 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 extracellular barium and cesium. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedKir2.1 channels play a key role in maintaining the correct resting potential in eukaryotic cells. Recently, specific amino acid mutations in the Kir2.1 inwardly rectifying potassium channel have been found to cause Andersen's Syndrome in humans. Here, we have characterized individual Andersen's Syndrome mutants R218Q, G300V, E303K, and delta314-315 and have found multiple effects on the ability of the cytoplasmic domains in Kir2.1 channels to form proper tetrameric assemblies. For the R218Q mutation, we identified a second site mutation (T309K) that restored tetrameric assembly but not function. We successfully crystallized and solved the structure (at 2.0 A) of the N- and C-terminal cytoplasmic domains of Kir2.1-R218Q/T309K(S). This new structure revealed multiple conformations of the G-loop and CD loop, providing an explanation for channels that assemble but do not conduct ions. Interestingly, Glu303 forms both intra- and intersubunit salt bridges, depending on the conformation of the G-loop, suggesting that the E303K mutant stabilizes both closed and open G-loop conformations. In the Kir2.1-R218Q/T309K(S) structure, we discovered that the DE loop forms a hydrophobic pocket that binds 2-methyl-2,4-pentanediol, which is located near the putative G(betagamma)-activation site of Kir3 channels. Finally, we observed a potassium ion bound to the cytoplasmic domain for this class of K+ channels. Andersen's syndrome mutation effects on the structure and assembly of the cytoplasmic domains of Kir2.1.,Pegan S, Arrabit C, Slesinger PA, Choe S Biochemistry. 2006 Jul 18;45(28):8599-606. PMID:16834334[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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