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X-ray crystal structure of a KirBac potassium channel highlights a mechanism of channel opening at the bundle-crossing gate.
Structural highlights
FunctionIRK10_MAGMG Inward rectifier potassium channel that mediates potassium uptake into the cell. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. The inward rectification may be achieved by the blockage of outward current by cytoplasmic divalent metal ions and polyamines. Complements an E.coli mutant that is defective in K(+) uptake.[1] [2] [3] Publication Abstract from PubMedKirBac channels are prokaryotic homologs of mammalian inwardly rectifying (Kir) potassium channels, and recent crystal structures of both Kir and KirBac channels have provided major insight into their unique structural architecture. However, all of the available structures are closed at the helix bundle crossing, and therefore the structural mechanisms that control opening of their primary activation gate remain unknown. In this study, we engineered the inner pore-lining helix (TM2) of KirBac3.1 to trap the bundle crossing in an apparently open conformation and determined the crystal structure of this mutant channel to 3.05 A resolution. Contrary to previous speculation, this new structure suggests a mechanistic model in which rotational 'twist' of the cytoplasmic domain is coupled to opening of the bundle-crossing gate through a network of inter- and intrasubunit interactions that involve the TM2 C-linker, slide helix, G-loop and the CD loop. Structure of a KirBac potassium channel with an open bundle crossing indicates a mechanism of channel gating.,Bavro VN, De Zorzi R, Schmidt MR, Muniz JR, Zubcevic L, Sansom MS, Venien-Bryan C, Tucker SJ Nat Struct Mol Biol. 2012 Jan 8;19(2):158-63. doi: 10.1038/nsmb.2208. PMID:22231399[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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