Abstract
The flow of ions through cation-selective members of the pentameric ligand-gated ion channel family is inhibited by a structurally diverse class of molecules that bind to the transmembrane pore in the open state of the protein. To obtain insight into the mechanism of channel block, we have investigated the binding of positively charged inhibitors to the open channel of the bacterial homolog GLIC by using X-ray crystallography and electrophysiology. Our studies reveal the location of two regions for interactions, with larger blockers binding in the center of the membrane and divalent transition metal ions binding to the narrow intracellular pore entry. The results provide a structural foundation for understanding the interactions of the channel with inhibitors that is relevant for the entire family.
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Acknowledgements
We would like to thank the staff of the X06SA beamline for support during data collection and members of the Dutzler lab for help in all stages of the project. Data collection was done at the Swiss Light Source of the Paul Scherrer Institute. The research leading to these results received funding from a grant from the Swiss National Science Foundation (SNF) and from an EC FP7 grant for the European Drug Initiative on Channels and Transporters consortium (HEALTH-201924). R.J.C.H. received the support of the Forschungskredit of the University of Zurich. C.B. and I.Z. are affiliated with the Biomolecular Structure and Mechanism PhD program of the University of Zurich (UZH) and the Swiss Federal Institute of Technology (ETH) Zurich.
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R.J.C.H. and C.B. carried out all experiments. I.Z. assisted in electrophysiological and crystallographic data collection. A.R. and D.T. synthesized the channel blockers. R.D., R.J.C.H. and C.B. jointly planned the experiments and analyzed the data. R.D. wrote the manuscript with the help of all coauthors.
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Hilf, R., Bertozzi, C., Zimmermann, I. et al. Structural basis of open channel block in a prokaryotic pentameric ligand-gated ion channel. Nat Struct Mol Biol 17, 1330–1336 (2010). https://doi.org/10.1038/nsmb.1933
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DOI: https://doi.org/10.1038/nsmb.1933