Journal article
cAMP binding to closed pacemaker ion channels is non-cooperative
Nature (London), Vol.595(7868), pp.606-610
07/22/2021
DOI: 10.1038/s41586-021-03686-x
PMCID: PMC8513821
PMID: 34194042
Abstract
Electrical activity in the brain and heart depends on rhythmic generation of action potentials by pacemaker ion channels (HCN) whose activity is regulated by cAMP binding(1). Previous work has uncovered evidence for both positive and negative cooperativity in cAMP binding(2,3), but such bulk measurements suffer from limited parameter resolution. Efforts to eliminate this ambiguity using single-molecule techniques have been hampered by the inability to directly monitor binding of individual ligand molecules to membrane receptors at physiological concentrations. Here we overcome these challenges using nanophotonic zero-mode waveguides(4) to directly resolve binding dynamics of individual ligands to multimeric HCN1 and HCN2 ion channels. We show that cAMP binds independently to all four subunits when the pore is closed, despite a subsequent conformational isomerization to a flip state at each site. The different dynamics in binding and isomerization are likely to underlie physiologically distinct responses of each isoform to cAMP5 and provide direct validation of the ligand-induced flip-state model(6-9). This approach for observing stepwise binding in multimeric proteins at physiologically relevant concentrations can directly probe binding allostery at single-molecule resolution in other intact membrane proteins and receptors.
Details
- Title: Subtitle
- cAMP binding to closed pacemaker ion channels is non-cooperative
- Creators
- David S. White - University of Wisconsin–MadisonSandipan Chowdhury - University of Wisconsin–MadisonVinay Idikuda - Washington University in St. LouisRuohan Zhang - University of Wisconsin–MadisonScott T. Retterer - Oak Ridge National LaboratoryRandall H. Goldsmith - University of Wisconsin–MadisonBaron Chanda - Washington University in St. Louis
- Resource Type
- Journal article
- Publication Details
- Nature (London), Vol.595(7868), pp.606-610
- DOI
- 10.1038/s41586-021-03686-x
- PMID
- 34194042
- PMCID
- PMC8513821
- NLM abbreviation
- Nature
- ISSN
- 0028-0836
- eISSN
- 1476-4687
- Publisher
- NATURE PORTFOLIO
- Number of pages
- 18
- Grant note
- CHE-1856518 / NSF; National Science Foundation (NSF) NS-116850; NS-101723; NS-081293; GM007507 / NIH; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA
- Language
- English
- Date published
- 07/22/2021
- Academic Unit
- Molecular Physiology and Biophysics
- Record Identifier
- 9984297596202771
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