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X-ray structure of a pentameric ligand-gated ion channel in an apparently open conformation

Abstract : Pentameric ligand-gated ion channels from the Cys-loop family mediate fast chemo-electrical transduction, but the mechanisms of ion permeation and gating of these membrane proteins remain elusive. Here we present the X-ray structure at 2.9 A resolution of the bacterial Gloeobacter violaceus pentameric ligand-gated ion channel homologue (GLIC) at pH 4.6 in an apparently open conformation. This cationic channel is known to be permanently activated by protons. The structure is arranged as a funnel-shaped transmembrane pore widely open on the outer side and lined by hydrophobic residues. On the inner side, a 5 A constriction matches with rings of hydrophilic residues that are likely to contribute to the ionic selectivity. Structural comparison with ELIC, a bacterial homologue from Erwinia chrysanthemi solved in a presumed closed conformation, shows a wider pore where the narrow hydrophobic constriction found in ELIC is removed. Comparative analysis of GLIC and ELIC reveals, in concert, a rotation of each extracellular beta-sandwich domain as a rigid body, interface rearrangements, and a reorganization of the transmembrane domain, involving a tilt of the M2 and M3 alpha-helices away from the pore axis. These data are consistent with a model of pore opening based on both quaternary twist and tertiary deformation.
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https://hal-pasteur.archives-ouvertes.fr/pasteur-02175132
Contributor : Marie de Tarragon <>
Submitted on : Friday, July 5, 2019 - 3:04:47 PM
Last modification on : Wednesday, September 23, 2020 - 4:34:02 AM

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Nicolas Bocquet, Hugues Nury, Marc Baaden, Chantal Le Poupon, Jean-Pierre Changeux, et al.. X-ray structure of a pentameric ligand-gated ion channel in an apparently open conformation. Nature, Nature Publishing Group, 2009, 457 (7225), pp.111-114. ⟨10.1038/nature07462⟩. ⟨pasteur-02175132⟩

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