6o9t
From Proteopedia
KirBac3.1 mutant at a resolution of 4.1 Angstroms
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 PubMedThe canonical mechanistic model explaining potassium channel gating is of a conformational change that alternately dilates and constricts a collar-like intracellular entrance to the pore. It is based on the premise that K(+) ions maintain a complete hydration shell while passing between the transmembrane cavity and cytosol, which must be accommodated. To put the canonical model to the test, we locked the conformation of a Kir K(+) channel to prevent widening of the narrow collar. Unexpectedly, conduction was unimpaired in the locked channels. In parallel, we employed all-atom molecular dynamics to simulate K(+) ions moving along the conduction pathway between the lower cavity and cytosol. During simulations, the constriction did not significantly widen. Instead, transient loss of some water molecules facilitated K(+) permeation through the collar. The low free energy barrier to partial dehydration in the absence of conformational change indicates Kir channels are not gated by the canonical mechanism. A constricted opening in Kir channels does not impede potassium conduction.,Black KA, He S, Jin R, Miller DM, Bolla JR, Clarke OB, Johnson P, Windley M, Burns CJ, Hill AP, Laver D, Robinson CV, Smith BJ, Gulbis JM Nat Commun. 2020 Jun 15;11(1):3024. doi: 10.1038/s41467-020-16842-0. PMID:32541684[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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