6U9Y

Wild-type MthK pore in 11 mM K+


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.80 Å
  • R-Value Free: 0.217 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.196 

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This is version 1.3 of the entry. See complete history


Literature

Selectivity filter ion binding affinity determines inactivation in a potassium channel.

Boiteux, C.Posson, D.J.Allen, T.W.Nimigean, C.M.

(2020) Proc Natl Acad Sci U S A 117: 29968-29978

  • DOI: https://doi.org/10.1073/pnas.2009624117
  • Primary Citation of Related Structures:  
    6U9P, 6U9T, 6U9Y, 6U9Z

  • PubMed Abstract: 

    Potassium channels can become nonconducting via inactivation at a gate inside the highly conserved selectivity filter (SF) region near the extracellular side of the membrane. In certain ligand-gated channels, such as BK channels and MthK, a Ca 2+ -activated K + channel from Methanobacterium thermoautotrophicum , the SF has been proposed to play a role in opening and closing rather than inactivation, although the underlying conformational changes are unknown. Using X-ray crystallography, identical conductive MthK structures were obtained in wide-ranging K + concentrations (6 to 150 mM), unlike KcsA, whose SF collapses at low permeant ion concentrations. Surprisingly, three of the SF's four binding sites remained almost fully occupied throughout this range, indicating high affinities (likely submillimolar), while only the central S2 site titrated, losing its ion at 6 mM, indicating low K + affinity (∼50 mM). Molecular simulations showed that the MthK SF can also collapse in the absence of K + , similar to KcsA, but that even a single K + binding at any of the SF sites, except S4, can rescue the conductive state. The uneven titration across binding sites differs from KcsA, where SF sites display a uniform decrease in occupancy with K + concentration, in the low millimolar range, leading to SF collapse. We found that ions were disfavored in MthK's S2 site due to weaker coordination by carbonyl groups, arising from different interactions with the pore helix and water behind the SF. We conclude that these differences in interactions endow the seemingly identical SFs of KcsA and MthK with strikingly different inactivating phenotypes.


  • Organizational Affiliation

    School of Science, RMIT University, Melbourne, VIC 3001, Australia.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Calcium-gated potassium channel MthK82Methanothermobacter thermautotrophicusMutation(s): 0 
Gene Names: mthKMTH_1520
Membrane Entity: Yes 
UniProt
Find proteins for O27564 (Methanothermobacter thermautotrophicus (strain ATCC 29096 / DSM 1053 / JCM 10044 / NBRC 100330 / Delta H))
Explore O27564 
Go to UniProtKB:  O27564
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO27564
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.80 Å
  • R-Value Free: 0.217 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.196 
  • Space Group: P 4 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 63.811α = 90
b = 63.811β = 90
c = 44.05γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
XDSdata reduction
PHENIXphasing
XDSdata scaling

Structure Validation

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Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesGM088352
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesF32GM087865

Revision History  (Full details and data files)

  • Version 1.0: 2020-11-04
    Type: Initial release
  • Version 1.1: 2020-11-18
    Changes: Database references
  • Version 1.2: 2020-12-09
    Changes: Database references
  • Version 1.3: 2023-10-11
    Changes: Data collection, Database references, Refinement description