title: A locally closed conformation of a bacterial pentameric proton-gated ion channel.
abstract: Pentameric ligand-gated ion channels mediate signal transduction through conformational transitions between closed-pore and open-pore states. To stabilize a closed conformation of GLIC, a bacterial proton-gated homolog from Gloeobacter violaceus whose open structure is known, we separately generated either four cross-links or two single mutations. We found all six mutants to be in the same 'locally closed' conformation using X-ray crystallography, sharing most of the features of the open form but showing a locally closed pore as a result of a concerted bending of all of its M2 helices. The mutants adopt several variant conformations of the M2-M3 loop, and in all cases an interacting lipid that is observed in the open form disappears. A single cross-linked mutant is functional, according to electrophysiology, and the locally closed structure of this mutant indicates that it has an increased flexibility. Further cross-linking, accessibility and molecular dynamics data suggest that the locally closed form is a functionally relevant conformation that occurs during allosteric gating transitions.
authors.affiliation: Institut Pasteur, Groupe Récepteurs-Canaux, Paris, France.
authors.forename: Marie S
authors.initials: MS
authors.lastname: Prevost
authors.forename: Ludovic
authors.initials: L
authors.lastname: Sauguet
authors.forename: Hugues
authors.initials: H
authors.lastname: Nury
authors.forename: Catherine
authors.initials: C
authors.lastname: Van Renterghem
authors.forename: Christèle
authors.initials: C
authors.lastname: Huon
authors.forename: Frederic
authors.initials: F
authors.lastname: Poitevin
authors.forename: Marc
authors.initials: M
authors.lastname: Baaden
authors.forename: Marc
authors.initials: M
authors.lastname: Delarue
authors.forename: Pierre-Jean
authors.initials: PJ
authors.lastname: Corringer
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D009154:Mutation; D011487:Protein Conformation; D011522:Protons
chemical_list: D001426:Bacterial Proteins; D007473:Ion Channels; D011522:Protons; D003545:Cysteine