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Open data
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Basic information
Entry | Database: EMDB / ID: EMD-20663 | |||||||||
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Title | MthK closed state with EDTA | |||||||||
![]() | MthK closed state with EDTA | |||||||||
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![]() | MthK / TRANSPORT PROTEIN | |||||||||
Function / homology | ![]() monoatomic cation transmembrane transporter activity / potassium ion transport / identical protein binding / metal ion binding / plasma membrane Similarity search - Function | |||||||||
Biological species | ![]() ![]() | |||||||||
Method | single particle reconstruction / cryo EM / Resolution: 3.6 Å | |||||||||
![]() | Fan C / Rheinberger J | |||||||||
![]() | ![]() Title: Ball-and-chain inactivation in a calcium-gated potassium channel. Authors: Chen Fan / Nattakan Sukomon / Emelie Flood / Jan Rheinberger / Toby W Allen / Crina M Nimigean / ![]() ![]() ![]() Abstract: Inactivation is the process by which ion channels terminate ion flux through their pores while the opening stimulus is still present. In neurons, inactivation of both sodium and potassium channels is ...Inactivation is the process by which ion channels terminate ion flux through their pores while the opening stimulus is still present. In neurons, inactivation of both sodium and potassium channels is crucial for the generation of action potentials and regulation of firing frequency. A cytoplasmic domain of either the channel or an accessory subunit is thought to plug the open pore to inactivate the channel via a 'ball-and-chain' mechanism. Here we use cryo-electron microscopy to identify the molecular gating mechanism in calcium-activated potassium channels by obtaining structures of the MthK channel from Methanobacterium thermoautotrophicum-a purely calcium-gated and inactivating channel-in a lipid environment. In the absence of Ca, we obtained a single structure in a closed state, which was shown by atomistic simulations to be highly flexible in lipid bilayers at ambient temperature, with large rocking motions of the gating ring and bending of pore-lining helices. In Ca-bound conditions, we obtained several structures, including multiple open-inactivated conformations, further indication of a highly dynamic protein. These different channel conformations are distinguished by rocking of the gating rings with respect to the transmembrane region, indicating symmetry breakage across the channel. Furthermore, in all conformations displaying open channel pores, the N terminus of one subunit of the channel tetramer sticks into the pore and plugs it, with free energy simulations showing that this is a strong interaction. Deletion of this N terminus leads to functionally non-inactivating channels and structures of open states without a pore plug, indicating that this previously unresolved N-terminal peptide is responsible for a ball-and-chain inactivation mechanism. | |||||||||
History |
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Structure visualization
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Structure viewer | EM map: ![]() ![]() ![]() |
Supplemental images |
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Downloads & links
-EMDB archive
Map data | ![]() | 5.6 MB | ![]() | |
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Header (meta data) | ![]() ![]() | 12.9 KB 12.9 KB | Display Display | ![]() |
Images | ![]() | 167.7 KB | ||
Filedesc metadata | ![]() | 5.2 KB | ||
Archive directory | ![]() ![]() | HTTPS FTP |
-Related structure data
Related structure data | ![]() 6u6dMC ![]() 6u5nC ![]() 6u5pC ![]() 6u5rC ![]() 6u68C ![]() 6u6eC ![]() 6u6hC ![]() 6uwnC ![]() 6ux4C ![]() 6ux7C ![]() 6uxaC ![]() 6uxbC C: citing same article ( M: atomic model generated by this map |
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Similar structure data |
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Links
EMDB pages | ![]() ![]() |
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Related items in Molecule of the Month |
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Map
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Annotation | MthK closed state with EDTA | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Voxel size | X=Y=Z: 1.059 Å | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Density |
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Symmetry | Space group: 1 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Details | EMDB XML:
CCP4 map header:
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-Supplemental data
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Sample components
-Entire : MthK in EDTA
Entire | Name: MthK in EDTA |
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Components |
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-Supramolecule #1: MthK in EDTA
Supramolecule | Name: MthK in EDTA / type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1 |
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Source (natural) | Organism: ![]() ![]() |
-Macromolecule #1: Calcium-gated potassium channel MthK
Macromolecule | Name: Calcium-gated potassium channel MthK / type: protein_or_peptide / ID: 1 / Number of copies: 8 / Enantiomer: LEVO |
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Source (natural) | Organism: ![]() ![]() |
Molecular weight | Theoretical: 37.35616 KDa |
Recombinant expression | Organism: ![]() ![]() |
Sequence | String: MVLVIEIIRK HLPRVLKVPA TRILLLVLAV IIYGTAGFHF IEGESWTVSL YWTFVTIATV GYGDYSPSTP LGMYFTVTLI VLGIGTFAV AVERLLEFLI NREQMKLMGL IDVAKSRHVV ICGWSESTLE CLRELRGSEV FVLAEDENVR KKVLRSGANF V HGDPTRVS ...String: MVLVIEIIRK HLPRVLKVPA TRILLLVLAV IIYGTAGFHF IEGESWTVSL YWTFVTIATV GYGDYSPSTP LGMYFTVTLI VLGIGTFAV AVERLLEFLI NREQMKLMGL IDVAKSRHVV ICGWSESTLE CLRELRGSEV FVLAEDENVR KKVLRSGANF V HGDPTRVS DLEKANVRGA RAVIVDLESD SETIHCILGI RKIDESVRII AEAERYENIE QLRMAGADQV ISPFVISGRL MS RSIDDGY EAMFVQDVLA EESTRRMVEV PIPEGSKLEG VSVLDADIHD VTGVIIIGVG RGDELIIDPP RDYSFRAGDI ILG IGKPEE IERLKNYISA UniProtKB: Calcium-gated potassium channel MthK |
-Macromolecule #2: POTASSIUM ION
Macromolecule | Name: POTASSIUM ION / type: ligand / ID: 2 / Number of copies: 2 / Formula: K |
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Molecular weight | Theoretical: 39.098 Da |
-Experimental details
-Structure determination
Method | cryo EM |
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![]() | single particle reconstruction |
Aggregation state | particle |
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Sample preparation
Buffer | pH: 7.5 Component:
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Grid | Model: Quantifoil, UltrAuFoil, R1.2/1.3 / Material: GOLD / Mesh: 300 | ||||||||||||
Vitrification | Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 296 K / Instrument: FEI VITROBOT MARK IV / Details: blotting for 2 s (blot force 0). |
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Electron microscopy
Microscope | FEI TITAN KRIOS |
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Image recording | Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Detector mode: SUPER-RESOLUTION / Average exposure time: 7.0 sec. / Average electron dose: 49.32 e/Å2 |
Electron beam | Acceleration voltage: 300 kV / Electron source: ![]() |
Electron optics | Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Nominal defocus max: 3.0 µm / Nominal defocus min: 0.5 µm |
Sample stage | Specimen holder model: FEI TITAN KRIOS AUTOGRID HOLDER |
Experimental equipment | ![]() Model: Titan Krios / Image courtesy: FEI Company |
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Image processing
Startup model | Type of model: INSILICO MODEL / Details: generated by cryoSPARC |
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Final reconstruction | Applied symmetry - Point group: C4 (4 fold cyclic) / Resolution.type: BY AUTHOR / Resolution: 3.6 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: RELION (ver. 3) / Number images used: 80904 |
Initial angle assignment | Type: PROJECTION MATCHING / Software - Name: cryoSPARC (ver. 2) |
Final angle assignment | Type: PROJECTION MATCHING / Software - Name: RELION (ver. 3) |