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Crystal Structure of the Cytoplasmic Domain of G-Protein-Gated Inward Rectifier Potassium Channel Kir3.2
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. 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 PubMedInward rectifier K+ (Kir) channels can be functionally categorized into two groups: those that are constitutively active and those that are constitutively inactive, with examples such as Kir2.x and Kir3.x, respectively. Their cytoplasmic regions are thought to be critical for control of channel gating, but a structural basis for this hypothesis is not known. In this study, we report a structure for the cytoplasmic region of a G protein-gated Kir channel, Kir3.2, and compare it with those of Kir3.1 and Kir2.1 channels. The isolated cytoplasmic region of Kir3.2 forms a tetrameric assembly in solution and also in the crystal. While the secondary structure arrangement and the subunit interface of the Kir3.2 crystal structure are found to be nearly identical to those of Kir3.1 and Kir2.1, it is quite different at and around loops between betaC- and betaD-strands and between betaH- and betaI-strands. These structural elements are located at the interface with the plasma membrane. Therefore, these structural elements could associate with the Kir channel transmembrane helices and be involved in the regulation of Kir channel gating. Structural diversity in the cytoplasmic region of G protein-gated inward rectifier K+ channels.,Inanobe A, Matsuura T, Nakagawa A, Kurachi Y Channels (Austin). 2007 Jan-Feb;1(1):39-45. Epub 2007 Jan 16. PMID:19151589[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||
