3eam | pdb_00003eam
An open-pore structure of a bacterial pentameric ligand-gated ion channel
Structural highlights
Function[GLIC_GLOVI] Cationic channel with similar permeabilities for Na(+) and K(+), that is activated by an increase of the proton concentration on the extracellular side. Displays no permeability for chloride ions. Shows slow kinetics of activation, no desensitization and a single channel conductance of 8 pS. Might contribute to adaptation to external pH change.[1] 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 PubMedPentameric 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. X-ray structure of a pentameric ligand-gated ion channel in an apparently open conformation.,Bocquet N, Nury H, Baaden M, Le Poupon C, Changeux JP, Delarue M, Corringer PJ Nature. 2009 Jan 1;457(7225):111-4. Epub 2008 Nov 5. PMID:18987633[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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