5LG3

X-ray structure of a pentameric ligand gated ion channel from Erwinia chrysanthemi (ELIC) in complex with chlorpromazine

Summary for 5LG3

• Entry DOI: 10.2210/pdb5lg3/pdb
• Descriptor: Gamma-aminobutyric-acid receptor subunit beta-1, 3-(2-chloro-10H-phenothiazin-10-yl)-N,N-dimethylpropan-1-amine (2 entities in total)
• Functional Keywords: ion channel, transport protein, membrane protein
• Biological source: Dickeya dadantii (strain 3937)
• Total number of polymer chains: 10
• Total formula weight: 357022.31

Authors

Nys, M.,Wijckmans, E.,Farinha, A.,Brams, M.,Spurny, R.,Ulens, C. (deposition date: 2016-07-05, release date: 2016-10-26, Last modification date: 2024-01-31)

Primary citation

Nys, M.,Wijckmans, E.,Farinha, A.,Yoluk, O.,Andersson, M.,Brams, M.,Spurny, R.,Peigneur, S.,Tytgat, J.,Lindahl, E.,Ulens, C.
Allosteric binding site in a Cys-loop receptor ligand-binding domain unveiled in the crystal structure of ELIC in complex with chlorpromazine.
Proc.Natl.Acad.Sci.USA, 113:E6696-E6703, 2016

PubMed Abstract: Pentameric ligand-gated ion channels or Cys-loop receptors are responsible for fast inhibitory or excitatory synaptic transmission. The antipsychotic compound chlorpromazine is a widely used tool to probe the ion channel pore of the nicotinic acetylcholine receptor, which is a prototypical Cys-loop receptor. In this study, we determine the molecular determinants of chlorpromazine binding in the Erwinia ligand-gated ion channel (ELIC). We report the X-ray crystal structures of ELIC in complex with chlorpromazine or its brominated derivative bromopromazine. Unexpectedly, we do not find a chlorpromazine molecule in the channel pore of ELIC, but behind the β8-β9 loop in the extracellular ligand-binding domain. The β8-β9 loop is localized downstream from the neurotransmitter binding site and plays an important role in coupling of ligand binding to channel opening. In combination with electrophysiological recordings from ELIC cysteine mutants and a thiol-reactive derivative of chlorpromazine, we demonstrate that chlorpromazine binding at the β8-β9 loop is responsible for receptor inhibition. We further use molecular-dynamics simulations to support the X-ray data and mutagenesis experiments. Together, these data unveil an allosteric binding site in the extracellular ligand-binding domain of ELIC. Our results extend on previous observations and further substantiate our understanding of a multisite model for allosteric modulation of Cys-loop receptors.

PubMed: 27791038
DOI: 10.1073/pnas.1603101113

Experimental method

X-RAY DIFFRACTION (3.567 Å)