RT Journal Article
SR Electronic
T1 Ligand-induced motions in pentameric ligand-gated ion channels revealed by EPR spectroscopy
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.11.04.368233
DO 10.1101/2020.11.04.368233
A1 Varun Tiwari
A1 Jennifer Borchardt
A1 Abby Schuh
A1 Candice S. Klug
A1 Cynthia Czajkowski
YR 2020
UL http://biorxiv.org/content/early/2020/11/05/2020.11.04.368233.abstract
AB Signaling in the brain depends on rapid opening and closing of pentameric ligand-gated ion channels (pLGICs). These proteins are the targets of various clinical drugs and, defects in their function is linked to a variety of diseases including myasthenia, epilepsy and sleep-disorders. While recent high-resolution structures of prokaryotic and eukaryotic pLGICs have shed light on the molecular architecture of these proteins, describing their conformational dynamics in physiological lipids is essential for understanding their function. Here, we used site-directed spin labeling electron paramagnetic resonance (SDSL EPR) spectroscopy and functional channels reconstituted in liposomes to reveal ligand-induced structural changes in the extracellular domain (ECD) of GLIC. Proton-activation caused an inward motion of labeled sites at the top of β-strands (β1, 2, 5, 6, 8) towards the channel lumen, consistent with an agonist-induced inward tilting motion of the ECD. Similar proton-dependent GLIC ECD motions were detected in the presence of a non-activating (gating deficient) mutation, suggesting that the inward tilting of the ECD does not accompany channel opening but is associated with an agonist-induced closed pre-activated channel state. These findings provide new insights into the protein dynamics underlying pLGIC gating transitions.Competing Interest StatementThe authors have declared no competing interest.