title: A structural, functional, and computational analysis suggests pore flexibility as the base for the poor selectivity of CNG channels.
abstract: Cyclic nucleotide-gated (CNG) ion channels, despite a significant homology with the highly selective K(+) channels, do not discriminate among monovalent alkali cations and are permeable also to several organic cations. We combined electrophysiology, molecular dynamics (MD) simulations, and X-ray crystallography to demonstrate that the pore of CNG channels is highly flexible. When a CNG mimic is crystallized in the presence of a variety of monovalent cations, including Na(+), Cs(+), and dimethylammonium (DMA(+)), the side chain of Glu66 in the selectivity filter shows multiple conformations and the diameter of the pore changes significantly. MD simulations indicate that Glu66 and the prolines in the outer vestibule undergo large fluctuations, which are modulated by the ionic species and the voltage. This flexibility underlies the coupling between gating and permeation and the poor ionic selectivity of CNG channels.
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy;
authors.forename: Luisa Maria Rosaria
authors.initials: LM
authors.lastname: Napolitano
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy;
authors.forename: Ina
authors.initials: I
authors.lastname: Bisha
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy;
authors.forename: Matteo
authors.initials: M
authors.lastname: De March
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy;
authors.forename: Arin
authors.initials: A
authors.lastname: Marchesi
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy;
authors.forename: Manuel
authors.initials: M
authors.lastname: Arcangeletti
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy;
authors.forename: Nicola
authors.initials: N
authors.lastname: Demitri
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy;
authors.forename: Monica
authors.initials: M
authors.lastname: Mazzolini
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy;
authors.forename: Alex
authors.initials: A
authors.lastname: Rodriguez
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy; National Research Council-Institute of Materials (CNR-IOM)-Democritos National Simulation Center c/o International School for Advanced Studies, Trieste 34136, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Magistrato
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste 34149, Italy; torre@sissa.it laio@sissa.it silvia.onesti@elettra.eu.
authors.forename: Silvia
authors.initials: S
authors.lastname: Onesti
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy; torre@sissa.it laio@sissa.it silvia.onesti@elettra.eu.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Laio
authors.affiliation: International School for Advanced Studies, Trieste 34136, Italy; torre@sissa.it laio@sissa.it silvia.onesti@elettra.eu.
authors.forename: Vincent
authors.initials: V
authors.lastname: Torre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002414:Cations, Monovalent / Q000378:metabolism; D002417:Cattle; D002586:Cesium / Q000378:metabolism; D018360:Crystallography, X-Ray; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D020125:Mutation, Missense; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D001426:Bacterial Proteins; C475741:CNGA1 protein, bovine; D002414:Cations, Monovalent; D054815:Cyclic Nucleotide-Gated Cation Channels; D050505:Mutant Proteins; D002586:Cesium; D012964:Sodium
keywords: CNG channels; MD simulations; X-ray crystallography; pore flexibility