3auw
From Proteopedia
Cytoplasmic domain of inward rectifier potassium channel Kir3.2 in complex with cadmium
Structural highlights
DiseaseKCNJ6_MOUSE Defects in Kcnj6 are the cause of the weaver (wv) phenotype. Homozygous animals suffer from severe ataxia that is obvious by about the second postnatal week. The cerebellum of these animals is drastically reduced in size due to depletion of the major cell type of cerebellum, the granule cell neuron. Heterozygous animals are not ataxic but have an intermediate number of surviving granule cells. Male homozygotes are sterile, because of complete failure of sperm production. Both hetero- and homozygous animals undergo sporadic tonic-clonic seizures. FunctionKCNJ6_MOUSE This potassium channel is controlled by G proteins. It plays a role in granule cell differentiation, possibly via membrane hyperpolarization. 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. Publication Abstract from PubMedThe gate at the pore-forming domain of potassium channels is allosterically controlled by a stimulus-sensing domain. Using Cd(2)(+) as a probe, we examined the structural elements responsible for gating in an inward-rectifier K(+) channel (Kir3.2). One of four endogenous cysteines facing the cytoplasm contributes to a high-affinity site for inhibition by internal Cd(2)(+). Crystal structure of its cytoplasmic domain in complex with Cd(2)(+) reveals that octahedral coordination geometry supports the high-affinity binding. This mode of action causes the tethering of the N-terminus to CD loop in the stimulus-sensing domain, suggesting that their conformational changes participate in gating and Cd(2)(+) inhibits Kir3.2 by trapping the conformation in the closed state like "inverse agonist". Inverse agonist-like action of cadmium on G-protein-gated inward-rectifier K(+) channels.,Inanobe A, Matsuura T, Nakagawa A, Kurachi Y Biochem Biophys Res Commun. 2011 Apr 8;407(2):366-71. Epub 2011 Mar 17. PMID:21396912[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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