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Elife. 2017 Mar 15;6. pii: e23955. doi: 10.7554/eLife.23955.

Identification of a pre-active conformation of a pentameric channel receptor.

Author information

1
Channel Receptors Unit, Institut Pasteur, Paris, France.
2
Unité Mixte de Recherche 3571, Centre National de la Recherche Scientifique, Paris, France.
3
Université Pierre et Marie Curie, Cellule Pasteur, Paris, France.
4
Departments of Anesthesiology, Physiology and Biophysics, Biochemistry, Weill Cornell Medicine, New York, United States.
5
BioCIS, Université Paris-Sud, CNRS, Université Paris-Saclay, Châtenay-Malabry, France.
6
Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, Paris, France.
7
Unité Mixte de Recherche 3528, Centre National de la Recherche Scientifique, Paris, France.
8
Biologie Cellulaire de la Synapse, Institute of Biology, Ecole Normale Supérieure, Paris, France.

Abstract

Pentameric ligand-gated ion channels (pLGICs) mediate fast chemical signaling through global allosteric transitions. Despite the existence of several high-resolution structures of pLGICs, their dynamical properties remain elusive. Using the proton-gated channel GLIC, we engineered multiple fluorescent reporters, each incorporating a bimane and a tryptophan/tyrosine, whose close distance causes fluorescence quenching. We show that proton application causes a global compaction of the extracellular subunit interface, coupled to an outward motion of the M2-M3 loop near the channel gate. These movements are highly similar in lipid vesicles and detergent micelles. These reorganizations are essentially completed within 2 ms and occur without channel opening at low proton concentration, indicating that they report a pre-active intermediate state in the transition pathway toward activation. This provides a template to investigate the gating of eukaryotic neurotransmitter receptors, for which intermediate states also participate in activation.

KEYWORDS:

allostery; biophysics; fluorescence; ligand-gated ion channels; neuroscience; none; structural biology

PMID:
28294942
PMCID:
PMC5398890
DOI:
10.7554/eLife.23955
[Indexed for MEDLINE]
Free PMC Article

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