Channel Receptors Unit, Institut Pasteur, Paris, France; Unité Mixte de Recherche 3571, Centre National de la Recherche Scientifique, Paris, France; Université Pierre et Marie Curie, Cellule Pasteur, Paris, France
Solène N Lefebvre
Channel Receptors Unit, Institut Pasteur, Paris, France; Unité Mixte de Recherche 3571, Centre National de la Recherche Scientifique, Paris, France; Université Pierre et Marie Curie, Cellule Pasteur, Paris, France
Philipp AM Schmidpeter
Departments of Anesthesiology, Physiology and Biophysics, Biochemistry, Weill Cornell Medicine, New York, United States
Emmanuelle Drège
BioCIS, Université Paris-Sud, CNRS, Université Paris-Saclay, Châtenay-Malabry, France
Zaineb Fourati
Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, Paris, France; Unité Mixte de Recherche 3528, Centre National de la Recherche Scientifique, Paris, France
Marc Delarue
Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, Paris, France; Unité Mixte de Recherche 3528, Centre National de la Recherche Scientifique, Paris, France
Stuart J Edelstein
Biologie Cellulaire de la Synapse, Institute of Biology, Ecole Normale Supérieure, Paris, France
Crina M Nimigean
Departments of Anesthesiology, Physiology and Biophysics, Biochemistry, Weill Cornell Medicine, New York, United States
Delphine Joseph
BioCIS, Université Paris-Sud, CNRS, Université Paris-Saclay, Châtenay-Malabry, France
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.
