title: Inhibition versus potentiation of ligand-gated ion channels can be altered by a single mutation that moves ligands between intra- and intersubunit sites.
abstract: Pentameric ligand-gated ion channels (pLGICs) are similar in structure but either inhibited or potentiated by alcohols and anesthetics. This dual modulation has previously not been understood, but the determination of X-ray structures of prokaryotic GLIC provides an ideal model system. Here, we show that a single-site mutation at the F14' site in the GLIC transmembrane domain turns desflurane and chloroform from inhibitors to potentiators, and that this is explained by competing allosteric sites. The F14'A mutation opens an intersubunit site lined by N239 (15'), I240 (16'), and Y263. Free energy calculations confirm this site is the preferred binding location for desflurane and chloroform in GLIC F14'A. In contrast, both anesthetics prefer an intrasubunit site in wild-type GLIC. Modulation is therefore the net effect of competitive binding between the intersubunit potentiating site and an intrasubunit inhibitory site. This provides direct evidence for a dual-site model of allosteric regulation of pLGICs.
authors.affiliation: Science for Life Laboratory, KTH Royal Institute of Technology & Stockholm University, 17121 Solna, Sweden.
authors.forename: Torben
authors.initials: T
authors.lastname: Brömstrup
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Howard
authors.forename: James R
authors.initials: JR
authors.lastname: Trudell
authors.forename: R Adron
authors.initials: RA
authors.lastname: Harris
authors.forename: Erik
authors.initials: E
authors.lastname: Lindahl
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002725:Chloroform / Q000494:pharmacology; D000458:Cyanobacteria; D000077335:Desflurane; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007530:Isoflurane / Q000031:analogs & derivatives / Q000494:pharmacology; D058446:Ligand-Gated Ion Channels / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D014982:Xenopus laevis
chemical_list: D018685:Anesthetics, Inhalation; D001426:Bacterial Proteins; D058446:Ligand-Gated Ion Channels; D021122:Protein Subunits; D002725:Chloroform; D000077335:Desflurane; D007530:Isoflurane
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