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Related Concept Videos

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Related Experiment Video

Updated: Jul 17, 2025

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins
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Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins

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Structural basis for ion selectivity in potassium-selective channelrhodopsins.

Seiya Tajima1, Yoon Seok Kim2, Masahiro Fukuda1

  • 1Komaba Institute for Science, The University of Tokyo, Meguro, Tokyo, Japan.

Cell
|August 31, 2023
PubMed
Summary
This summary is machine-generated.

K+-selective light-gated ion channels (KCRs) achieve selectivity via a unique asymmetric gate, not a canonical filter. This discovery enables next-generation optogenetic tools for research and therapeutic applications.

Keywords:
HcKCRMD simulationchannelrhodopsincryo-EMelectrophysiologymicrobial opsinoptogeneticspotassium channelspectroscopystructure-guided engineering

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Area of Science:

  • Structural biology
  • Optogenetics
  • Ion channel biophysics

Background:

  • KCR channelrhodopsins are promising inhibitory optogenetic tools.
  • The mechanism of K+ selectivity in KCRs remains poorly understood.

Purpose of the Study:

  • To elucidate the structural basis of K+ selectivity in KCRs.
  • To understand the mechanism of ion conduction and gating.
  • To engineer KCR variants with enhanced K+ selectivity for optogenetics.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) at 2.5-2.7 Å resolution.
  • Electrophysiology, computational modeling, spectroscopy, and biochemical assays.
  • Structure-guided mutagenesis to enhance K+ selectivity.

Main Results:

  • Determined high-resolution structures of HcKCR1, HcKCR2, and a selectivity-enhanced mutant.
  • Revealed a novel K+ selectivity mechanism involving an asymmetric extracellular gate and an intracellular dehydration pathway.
  • Identified structural basis for spectral differences and engineered KALI-1/KALI-2 variants with improved K+ selectivity.

Conclusions:

  • The KCR K+ selectivity mechanism differs fundamentally from canonical K+ channels.
  • Structural insights provide a foundation for developing advanced optogenetic tools.
  • Engineered KCR variants offer enhanced performance for optogenetic inhibition in vitro and in vivo.