Structural dynamics in the gating ring of cyclic nucleotide-gated ion channels.
For ligand-gated ion channels, the binding of a ligand to an intracellular or extracellular domain generates changes in transmembrane pore-forming helices, which alters ion flow. The molecular mechanism for this allostery, however, remains unknown. Here we explore the structure and conformational rearrangements of the C-terminal gating ring of the cyclic nucleotide-gated channel CNGA1 during activation by cyclic nucleotides with patch-clamp fluorometry. By monitoring fluorescent resonance energy transfer (FRET) between membrane-resident quenchers and fluorophores attached to the channel, we detected no movement orthogonal to the membrane during channel activation. By monitoring FRET between fluorophores within the C-terminal region, we determined that the C-terminal end of the C-linker and the end of the C-helix move apart when channels open. We conclude that during channel activation, a portion of the gating ring moves parallel to the plasma membrane, hinging toward the central axis of the channel.
Taraska
Justin W
JW
Department of Physiology and Biophysics, Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA.
Zagotta
William N
WN
D000494:Allosteric Regulation; D031541:Fluorescence Resonance Energy Transfer; D015640:Ion Channel Gating; D015335:Molecular Probes; D009711:Nucleotides / Q000737:chemistry*; D011487:Protein Conformation
D015335:Molecular Probes; D009711:Nucleotides