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- PDB-9pkp: Structure of the two-pore domain, outwardly rectifying potassium ... -

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Basic information

Entry
Database: PDB / ID: 9pkp
TitleStructure of the two-pore domain, outwardly rectifying potassium (TOK1) from Candida albicans, Down conformation
ComponentsTOK potassium channel
KeywordsMETAL TRANSPORT / potassium ion channel
Function / homologystabilization of membrane potential / potassium ion leak channel activity / Two pore domain potassium channel / outward rectifier potassium channel activity / Potassium channel domain / Ion channel / plasma membrane / : / TOK potassium channel
Function and homology information
Biological speciesCandida albicans (yeast)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.05 Å
AuthorsDurocher, B. / Manville, R.W. / Yan, R. / Yu, Z. / Abbott, G.W. / Miller, A.N.
Funding support1items
OrganizationGrant numberCountry
Not funded
CitationJournal: Nat Commun / Year: 2026
Title: Molecular architecture of the fungal-specific potassium channel TOK1.
Authors: Brice Durocher / Rían W Manville / Rui Yan / Zhiheng Yu / Geoffrey W Abbott / Alexandria N Miller /
Abstract: In Candida albicans, potassium (K) channels fine-tune ionic balance under stress, contributing to host colonization. Fungal two-pore domain, outwardly rectifying potassium (TOK) channels remain ...In Candida albicans, potassium (K) channels fine-tune ionic balance under stress, contributing to host colonization. Fungal two-pore domain, outwardly rectifying potassium (TOK) channels remain insufficiently characterized despite evidence implicating them in growth and viability. Here, we describe the atomic-resolution structure of a fungal potassium channel, TOK1 from C. albicans (CaTOK), revealing an architecture defined by eight transmembrane helices and a membrane topology distinct from previously characterized K⁺ channel classes. The first four helices form a tetraspanin-like bundle resembling auxiliary subunits of human neuronal ion channels. The pore features an inner helical gating movement analogous to mammalian dimeric K channels, while the K selectivity filter exhibits atypical ion coordination. A cytosolic C-terminal bundle forms an intramolecular network that likely stabilizes CaTOK and may mediate gating. These findings provide a framework for understanding TOK channel function and facilitate future studies of fungal ion homeostasis, pathogenicity, and therapeutic development.
History
DepositionJul 14, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0Apr 29, 2026Provider: repository / Type: Initial release
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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

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Assembly

Deposited unit
A: TOK potassium channel
B: TOK potassium channel
hetero molecules


Theoretical massNumber of molelcules
Total (without water)202,10952
Polymers177,5212
Non-polymers24,58850
Water00
1


  • Idetical with deposited unit
  • defined by author&software
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_555x,y,z1

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Components

#1: Protein TOK potassium channel


Mass: 88760.570 Da / Num. of mol.: 2
Source method: isolated from a genetically manipulated source
Details: C-terminal HRV 3C Twin strep tag / Source: (gene. exp.) Candida albicans (yeast) / Production host: Spodoptera frugiperda (fall armyworm) / References: UniProt: C0IRA7
#2: Chemical ChemComp-K / POTASSIUM ION


Mass: 39.098 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: K / Feature type: SUBJECT OF INVESTIGATION
#3: Sugar...
ChemComp-LMT / DODECYL-BETA-D-MALTOSIDE


Type: D-saccharide / Mass: 510.615 Da / Num. of mol.: 48 / Source method: obtained synthetically / Formula: C24H46O11 / Comment: detergent*YM
Has ligand of interestY
Has protein modificationN

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: Candida albicans two-pore domain, outward rectifying potassium channel 1 (TOK1)
Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT
Source (natural)Organism: Candida albicans (yeast)
Source (recombinant)Organism: Spodoptera frugiperda (fall armyworm)
Buffer solutionpH: 7
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: TFS KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal defocus max: 2000 nm / Nominal defocus min: 800 nm
Image recordingElectron dose: 50 e/Å2 / Film or detector model: GATAN K3 (6k x 4k)

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Processing

EM software
IDNameCategory
1RELIONparticle selection
13cryoSPARC3D reconstruction
CTF correctionType: NONE
3D reconstructionResolution: 3.05 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 144497 / Symmetry type: POINT

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