Ligand discrimination and gating in cyclic nucleotide-gated ion channels from apo and partial agonist-bound cryo-EM structures

  1. Jan Rheinberger
  2. Xiaolong Gao
  3. Philipp AM Schmidpeter
  4. Crina M Nimigean  Is a corresponding author
  1. Weill Cornell Medical College, United States

Abstract

Cyclic nucleotide-modulated channels have important roles in visual signal transduction and pacemaking. Binding of cyclic nucleotides (cAMP/cGMP) elicits diverse functional responses in different channels within the family despite their high sequence and structure homology. The molecular mechanisms responsible for ligand discrimination and gating are unknown due to lack of correspondence between structural information and functional states. Using single particle cryo-electron microscopy and single-channel recording, we assigned functional states to high-resolution structures of SthK, a prokaryotic cyclic nucleotide-gated channel. The structures for apo, cAMP-bound, and cGMP-bound SthK in lipid nanodiscs, correspond to no, moderate, and low single-channel activity, respectively, consistent with the observation that all structures are in resting, closed states. The similarity between apo and ligand-bound structures indicates that ligand-binding domains are strongly coupled to pore and SthK gates in an allosteric, concerted fashion. The different orientations of cAMP and cGMP in the 'resting' and 'activated' structures suggest a mechanism for ligand discrimination.

Data availability

The 3 density maps and 3 atomic models have been deposited in PDB under the following accession codes: 6CJQ, 6CJU and 6CJT (coordinates of atomic models), EMD-7482, EMD-7484 and EMD-7483 (density maps).

The following data sets were generated

Article and author information

Author details

  1. Jan Rheinberger

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-9901-2065
  2. Xiaolong Gao

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Philipp AM Schmidpeter

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2871-9706
  4. Crina M Nimigean

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    For correspondence
    crn2002@med.cornell.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6254-4447

Funding

National Institute of General Medical Sciences (R01GM124451 and R01GM088352)

  • Crina M Nimigean

Deutsche Forschungsgemeinschaft (SCHM 3198/1-1)

  • Philipp AM Schmidpeter

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Richard Aldrich, The University of Texas at Austin, United States

Publication history

  1. Received: July 2, 2018
  2. Accepted: July 19, 2018
  3. Accepted Manuscript published: July 20, 2018 (version 1)
  4. Version of Record published: August 15, 2018 (version 2)

Copyright

© 2018, Rheinberger et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Jan Rheinberger
  2. Xiaolong Gao
  3. Philipp AM Schmidpeter
  4. Crina M Nimigean
(2018)
Ligand discrimination and gating in cyclic nucleotide-gated ion channels from apo and partial agonist-bound cryo-EM structures
eLife 7:e39775.
https://doi.org/10.7554/eLife.39775
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