Subunit interactions in the activation of cyclic nucleotide-gated ion channels

M D Varnum; W N Zagotta

doi:10.1016/S0006-3495(96)79836-3

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Subunit interactions in the activation of cyclic nucleotide-gated ion channels

Journal article

Open access

Peer reviewed

Subunit interactions in the activation of cyclic nucleotide-gated ion channels

M D Varnum and W N Zagotta

Biophysical journal, Vol.70(6), pp.2667-2679

06/1996

DOI: https://doi.org/10.1016/S0006-3495(96)79836-3

Handle:

https://hdl.handle.net/2376/116474

PMCID: PMC1225246

PMID: 8744304

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https://doi.org/10.1016/S0006-3495(96)79836-3View

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Abstract

Allosteric Site - genetics

Nucleotides, Cyclic - metabolism

Recombinant Proteins - metabolism

Biophysical Phenomena

Mutagenesis, Site-Directed

Ion Channels - genetics

Recombinant Proteins - chemistry

Recombinant Proteins - genetics

Biophysics

Retinal Rod Photoreceptor Cells - metabolism

Animals

Ion Channels - metabolism

Cattle

Models, Biological

Protein Conformation

In Vitro Techniques

Dimerization

Ion Channel Gating

Ion Channels - chemistry

Cyclic nucleotide-gated (CNG) ion channels of retinal photoreceptors and olfactory neurons are multimeric proteins of unknown stoichiometry. To investigate the subunit interactions that occur during CNG channel activation, we have used tandem cDNA constructs of the rod CNG channel to generate heteromultimeric channels composed of wild-type and mutant subunits. We introduced point mutations that affect channel activation: 1) D604M, which alters the relative ability of agonists to promote the allosteric conformational change(s) associated with channel opening, and 2) T560A, which primarily affects the initial binding affinity for cGMP, and to a lesser extent, the allosteric transition. At saturating concentrations of agonist, heteromultimeric channels were intermediate between wild-type and mutant homomultimers in agonist efficacy and apparent affinity for cGMP, cIMP, and cAMP, consistent with a model for the allosteric transition involving a concerted conformational change in all of the channel subunits. Results were also consistent with a model involving independent transitions in two or three, but not one or four, of the channel subunits. The behavior of the heterodimers implies that the channel stoichiometry is some multiple of 2 and is consistent with a tetrameric quaternary structure for the functional channel complex. Steady-state dose-response relations for homomultimeric and heteromultimeric channels were well fit by a Monod, Wyman, and Changeux model with a concerted allosteric opening transition stabilized by binding of agonist.

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Details

Title: Subunit interactions in the activation of cyclic nucleotide-gated ion channels
Creators: M D Varnum - Department of Physiology and Biophysics, Howard Hughes Medical Institute, University of Washington, Seattle 98195, USA
W N Zagotta
Publication Details: Biophysical journal, Vol.70(6), pp.2667-2679
Academic Unit: Integrative Physiology and Neuroscience, Department of
Publisher: United States
Grant note: R01 EY010329 / NEI NIH HHS EY 10329 / NEI NIH HHS
Identifiers: 99900547330901842
Language: English
Resource Type: Journal article