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Principal pathway coupling agonist binding to channel gating in nicotinic receptors

Nature volume 438, pages 243–247 (2005)Cite this article

Abstract

Synaptic receptors respond to neurotransmitters by opening an intrinsic ion channel in the final step in synaptic transmission. How binding of the neurotransmitter is conveyed over the long distance to the channel remains a central question in neurobiology. Here we delineate a principal pathway that links neurotransmitter binding to channel gating by using a structural model of the Torpedo acetylcholine receptor at 4-Å resolution1, recordings of currents through single receptor channels and determinations of energetic coupling between pairs of residues. We show that a pair of invariant arginine and glutamate residues in each receptor α-subunit electrostatically links peripheral and inner β-sheets from the binding domain and positions them to engage with the channel. The key glutamate and flanking valine residues energetically couple to conserved proline and serine residues emerging from the top of the channel-forming α-helix, suggesting that this is the point at which the binding domain triggers opening of the channel. The series of interresidue couplings identified here constitutes a primary allosteric pathway that links neurotransmitter binding to channel gating.

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Figure 1: Structural model of the Torpedo receptor ligand-binding and pore domains at 4 Å resolution (PDB 2BG9) and proposed principal pathway linking agonist binding to channel gating.
Figure 2: Energetic coupling between Glu 45 and Arg 209 in the α-subunit.
Figure 3: Energetic coupling between residues in the α-subunit.

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Acknowledgements

We thank C. R. Free for contributions to the molecular biology and T. Therneau for help with statistical analysis. This work was supported by a grant from the NIH.

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Authors and Affiliations

  1. Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering,

    Won Yong Lee & Steven M. Sine

  2. Molecular Neuroscience Graduate Program, Mayo Clinic College of Medicine, Minnesota, 55905, Rochester, USA

    Won Yong Lee

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  1. Won Yong Lee
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Correspondence to Steven M. Sine.

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Supplementary information

Supplementary Methods

This is an additional information regarding the experimental methods not included in the main text. (DOC 26 kb)

Supplementary Table 1

Kinetic analysis of AChRs with mutations in the α-subunit. (DOC 81 kb)

Supplementary Table S2

Kinetic analysis of AChRs with mutations in non-α-subunits. (DOC 61 kb)

Supplementary Table S3

Sequence alignments of receptors in the Cys-loop superfamily. (DOC 41 kb)

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Lee, W., Sine, S. Principal pathway coupling agonist binding to channel gating in nicotinic receptors. Nature 438, 243–247 (2005). https://doi.org/10.1038/nature04156

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