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- PDB-8iu0: Cryo-EM structure of the potassium-selective channelrhodopsin HcK... -
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Open data
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Basic information
Entry | Database: PDB / ID: 8iu0 | ||||||||||||||||||||||||
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Title | Cryo-EM structure of the potassium-selective channelrhodopsin HcKCR1 H225F mutant in lipid nanodisc | ||||||||||||||||||||||||
![]() | HcKCR1 | ||||||||||||||||||||||||
![]() | MEMBRANE PROTEIN / Cryo-EM | ||||||||||||||||||||||||
Function / homology | Rhopdopsin 7-helix transmembrane proteins / Rhodopsin 7-helix transmembrane proteins / Up-down Bundle / Mainly Alpha / PALMITIC ACID / Chem-PSC / RETINAL![]() | ||||||||||||||||||||||||
Biological species | ![]() | ||||||||||||||||||||||||
Method | ELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.66 Å | ||||||||||||||||||||||||
![]() | Tajima, S. / Kim, Y. / Nakamura, S. / Yamashita, K. / Fukuda, M. / Deisseroth, K. / Kato, H.E. | ||||||||||||||||||||||||
Funding support | ![]()
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![]() | ![]() Title: Structural basis for ion selectivity in potassium-selective channelrhodopsins. Authors: Seiya Tajima / Yoon Seok Kim / Masahiro Fukuda / YoungJu Jo / Peter Y Wang / Joseph M Paggi / Masatoshi Inoue / Eamon F X Byrne / Koichiro E Kishi / Seiwa Nakamura / Charu Ramakrishnan / ...Authors: Seiya Tajima / Yoon Seok Kim / Masahiro Fukuda / YoungJu Jo / Peter Y Wang / Joseph M Paggi / Masatoshi Inoue / Eamon F X Byrne / Koichiro E Kishi / Seiwa Nakamura / Charu Ramakrishnan / Shunki Takaramoto / Takashi Nagata / Masae Konno / Masahiro Sugiura / Kota Katayama / Toshiki E Matsui / Keitaro Yamashita / Suhyang Kim / Hisako Ikeda / Jaeah Kim / Hideki Kandori / Ron O Dror / Keiichi Inoue / Karl Deisseroth / Hideaki E Kato / ![]() ![]() ![]() Abstract: KCR channelrhodopsins (K-selective light-gated ion channels) have received attention as potential inhibitory optogenetic tools but more broadly pose a fundamental mystery regarding how their K ...KCR channelrhodopsins (K-selective light-gated ion channels) have received attention as potential inhibitory optogenetic tools but more broadly pose a fundamental mystery regarding how their K selectivity is achieved. Here, we present 2.5-2.7 Å cryo-electron microscopy structures of HcKCR1 and HcKCR2 and of a structure-guided mutant with enhanced K selectivity. Structural, electrophysiological, computational, spectroscopic, and biochemical analyses reveal a distinctive mechanism for K selectivity; rather than forming the symmetrical filter of canonical K channels achieving both selectivity and dehydration, instead, three extracellular-vestibule residues within each monomer form a flexible asymmetric selectivity gate, while a distinct dehydration pathway extends intracellularly. Structural comparisons reveal a retinal-binding pocket that induces retinal rotation (accounting for HcKCR1/HcKCR2 spectral differences), and design of corresponding KCR variants with increased K selectivity (KALI-1/KALI-2) provides key advantages for optogenetic inhibition in vitro and in vivo. Thus, discovery of a mechanism for ion-channel K selectivity also provides a framework for next-generation optogenetics. | ||||||||||||||||||||||||
History |
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Structure visualization
Structure viewer | Molecule: ![]() ![]() |
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Downloads & links
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PDBx/mmCIF format | ![]() | 79.1 KB | Display | ![]() |
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PDB format | ![]() | 52.4 KB | Display | ![]() |
PDBx/mmJSON format | ![]() | Tree view | ![]() | |
Others | ![]() |
-Validation report
Summary document | ![]() | 1.6 MB | Display | ![]() |
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Full document | ![]() | 1.6 MB | Display | |
Data in XML | ![]() | 21.7 KB | Display | |
Data in CIF | ![]() | 28.4 KB | Display | |
Arichive directory | ![]() ![]() | HTTPS FTP |
-Related structure data
Related structure data | ![]() 35713MC ![]() 8h86C ![]() 8h87C M: map data used to model this data C: citing same article ( |
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Similar structure data | Similarity search - Function & homology ![]() |
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Links
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Assembly
Deposited unit | ![]()
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1 | ![]()
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2 |
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3 | ![]()
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Symmetry | Point symmetry: (Schoenflies symbol: C3 (3 fold cyclic)) | ||||||||||||||||
Noncrystallographic symmetry (NCS) | NCS oper:
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Components
#1: Protein | Mass: 31408.795 Da / Num. of mol.: 1 / Mutation: H225F Source method: isolated from a genetically manipulated source Source: (gene. exp.) ![]() ![]() ![]() | ||||||||
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#2: Chemical | ChemComp-RET / | ||||||||
#3: Chemical | ChemComp-PSC / ( #4: Chemical | ChemComp-PLM / #5: Water | ChemComp-HOH / | Has ligand of interest | Y | Has protein modification | Y | |
-Experimental details
-Experiment
Experiment | Method: ELECTRON MICROSCOPY |
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EM experiment | Aggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction |
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Sample preparation
Component | Name: HcKCR1 / Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT |
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Molecular weight | Experimental value: NO |
Source (natural) | Organism: ![]() |
Source (recombinant) | Organism: ![]() ![]() |
Buffer solution | pH: 7.5 |
Specimen | Embedding applied: YES / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES |
Specimen support | Grid material: GOLD / Grid mesh size: 300 divisions/in. / Grid type: Quantifoil R1.2/1.3 |
EM embedding | Details: nanodisc composed of MSP1D1E3 and soybean lipids / Material: Lipid |
Vitrification | Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 100 % / Chamber temperature: 277 K |
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Electron microscopy imaging
Experimental equipment | ![]() Model: Titan Krios / Image courtesy: FEI Company |
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Microscopy | Model: FEI TITAN KRIOS |
Electron gun | Electron source: ![]() |
Electron lens | Mode: BRIGHT FIELD / Nominal defocus max: 1600 nm / Nominal defocus min: 800 nm / Cs: 2.7 mm |
Image recording | Electron dose: 48 e/Å2 / Film or detector model: GATAN K3 (6k x 4k) |
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Processing
Software | Name: REFMAC / Version: 5.8.0403 / Classification: refinement | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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CTF correction | Type: PHASE FLIPPING AND AMPLITUDE CORRECTION | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Symmetry | Point symmetry: C3 (3 fold cyclic) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
3D reconstruction | Resolution: 2.66 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 180294 / Symmetry type: POINT | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Refinement | Resolution: 2.66→2.66 Å / Cor.coef. Fo:Fc: 0.806 / SU B: 5.969 / SU ML: 0.115 / ESU R: 0.154 Stereochemistry target values: MAXIMUM LIKELIHOOD WITH PHASES Details: HYDROGENS HAVE BEEN ADDED IN THE RIDING POSITIONS
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Solvent computation | Solvent model: PARAMETERS FOR MASK CACLULATION | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Displacement parameters | Biso mean: 60.218 Å2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Refinement step | Cycle: 1 / Total: 2354 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Refine LS restraints |
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