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bioRxiv · 10.1101/2020.06.19.161356

Characterization of the dynamic resting state of a pentameric ligand-gated ion channel by cryo-electron microscopy and simulations

Rovsnik, U.·Zhuang, Y.·Axelsson, L.·Forsberg, B. O.·Lim, V. T.·Carroni, M.·Blau, C.·Howard, R. J.·Lindahl, E.
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Abstract

Ligand-gated ion channels are critical mediators of electrochemical signal transduction across evolution. Biophysical and pharmacological development in this family relies on high-quality structural data in multiple, subtly distinct functional states. However, structural data remain limited, particularly for the unliganded or resting state. Here we report cryo-electron microscopy structures of the Gloeobacter violaceus ligand-gated ion channel (GLIC) under resting and activating conditions (neutral and low pH). Parallel models were built either manually or using recently developed density-guided molecular simulations. The moderate resolution of resting-state reconstructions, particularly in the extracellular domain, was improved under activating conditions, enabling the visualization of residues at key subunit interfaces including loops B, C, F, and M2-M3. Combined with molecular dynamics simulations, the cryo-electron microscopy structures at different pH describe a heterogeneous population of closed channels, with activating conditions condensing the closed-channel energy landscape on a pathway towards gating.

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Rovsnik, U., Zhuang, Y., Axelsson, L., Forsberg, B. O., Lim, V. T., Carroni, M., Blau, C., Howard, R. J., Lindahl, E.. 2020-06-20. Characterization of the dynamic resting state of a pentameric ligand-gated ion channel by cryo-electron microscopy and simulations. https://doi.org/10.1101/2020.06.19.161356

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