Hysteresis of ligand binding in CNGA2 ion channels

Vasilica Nache, Thomas Eick, Eckhard Schulz, Ralf Schmauder and Klaus Benndorf ()
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Vasilica Nache: Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena
Thomas Eick: Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena
Eckhard Schulz: Fachhochschule Schmalkalden, Fakultät Elektrotechnik
Ralf Schmauder: Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena
Klaus Benndorf: Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena

Nature Communications, 2013, vol. 4, issue 1, 1-9

Abstract: Abstract Tetrameric cyclic nucleotide-gated (CNG) channels mediate receptor potentials in olfaction and vision. The channels are activated by the binding of cyclic nucleotides to a binding domain embedded in the C terminus of each subunit. Here using a fluorescent cGMP derivative (fcGMP), we show for homotetrameric CNGA2 channels that ligand unbinding is ~50 times faster at saturating than at subsaturating fcGMP. Analysis with complex Markovian models reveals two pathways for ligand unbinding; the partially liganded open channel unbinds its ligands from closed states only, whereas the fully liganded channel reaches a different open state from which it unbinds all four ligands rapidly. Consequently, the transition pathways for ligand binding and activation of a fully liganded CNGA2 channel differ from that of ligand unbinding and deactivation, resulting in pronounced hysteresis of the gating mechanism. This concentration-dependent gating mechanism allows the channels to respond to changes in the cyclic nucleotide concentration with different kinetics.

Date: 2013
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DOI: 10.1038/ncomms3866

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