Multisite binding of a general anesthetic to the prokaryotic pentameric Erwinia chrysanthemi ligand-gated ion channel (ELIC)

J Biol Chem. 2013 Mar 22;288(12):8355-8364. doi: 10.1074/jbc.M112.424507. Epub 2013 Jan 30.

Abstract

Pentameric ligand-gated ion channels (pLGICs), such as nicotinic acetylcholine, glycine, γ-aminobutyric acid GABA(A/C) receptors, and the Gloeobacter violaceus ligand-gated ion channel (GLIC), are receptors that contain multiple allosteric binding sites for a variety of therapeutics, including general anesthetics. Here, we report the x-ray crystal structure of the Erwinia chrysanthemi ligand-gated ion channel (ELIC) in complex with a derivative of chloroform, which reveals important features of anesthetic recognition, involving multiple binding at three different sites. One site is located in the channel pore and equates with a noncompetitive inhibitor site found in many pLGICs. A second transmembrane site is novel and is located in the lower part of the transmembrane domain, at an interface formed between adjacent subunits. A third site is also novel and is located in the extracellular domain in a hydrophobic pocket between the β7-β10 strands. Together, these results extend our understanding of pLGIC modulation and reveal several specific binding interactions that may contribute to modulator recognition, further substantiating a multisite model of allosteric modulation in this family of ion channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Anesthetics, Inhalation / chemistry*
  • Animals
  • Bacterial Proteins / chemistry*
  • Binding Sites
  • Chloroform / chemistry
  • Chloroform / pharmacology
  • Crystallography, X-Ray
  • Dickeya chrysanthemi*
  • Ligand-Gated Ion Channels / chemistry*
  • Membrane Potentials / drug effects
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Oocytes / drug effects
  • Oocytes / metabolism
  • Oocytes / physiology
  • Patch-Clamp Techniques
  • Protein Binding
  • Protein Stability
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Receptors, Glycine / genetics
  • Receptors, Glycine / metabolism
  • Trihalomethanes / chemistry
  • Trihalomethanes / pharmacology
  • Xenopus laevis

Substances

  • Anesthetics, Inhalation
  • Bacterial Proteins
  • Ligand-Gated Ion Channels
  • Receptors, Glycine
  • Trihalomethanes
  • Chloroform
  • bromoform

Associated data

  • PDB/3ZKR