2AEM

Crystal Structures of the MthK RCK Domain


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.80 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.224 
  • R-Value Observed: 0.226 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Structures of the MthK RCK Domain and the Effect of Ca2+ on Gating Ring Stability

Dong, J.Shi, N.Berke, I.Chen, L.Jiang, Y.

(2005) J Biol Chem 280: 41716-41724

  • DOI: 10.1074/jbc.M508144200
  • Primary Citation of Related Structures:  
    2AEF, 2AEJ, 2AEM

  • PubMed Abstract: 
  • MthK is a Ca2+-gated K+ channel from Methanobacterium autotrophicum. The crystal structure of the MthK channel in a Ca2+-bound open state was previously determined at 3.3 A and revealed an octameric gating ring composed of eight intracellular ligand-binding RCK (regulate the conductance of K+) domains ...

    MthK is a Ca2+-gated K+ channel from Methanobacterium autotrophicum. The crystal structure of the MthK channel in a Ca2+-bound open state was previously determined at 3.3 A and revealed an octameric gating ring composed of eight intracellular ligand-binding RCK (regulate the conductance of K+) domains. It was suggested that Ca2+ binding regulates the gating ring conformation, which in turn leads to the opening and closing of the channel. However, at 3.3 AA resolution, the molecular details of the structure are not well defined, and many of the conclusions drawn from that structure were hypothetical. Here we have presented high resolution structures of the MthK RCK domain with and without Ca2+ bound from three different crystals. These structures revealed a dimeric architecture of the RCK domain and allowed us to visualize the Ca2+ binding and protein-protein contacts at atomic detail. The dimerization of RCK domains is also conserved in other RCK-regulated K+ channels and transporters, suggesting that the RCK dimer serves as a basic unit in the gating ring assembly. A comparison of these dimer structures confirmed that the dimer interface is indeed flexible as suggested previously. However, the conformational change at the flexible interface is of an extent smaller than the previously hypothesized gating ring movement, and a reconstruction of these dimers into octamers by applying protein-protein contacts at the fixed interface did not generate enclosed gating rings. This indicated that there is a high probability that the previously defined fixed interface may not be fixed during channel gating. In addition to the structural studies, we have also carried out biochemical analyses and have shown that near physiological pH, isolated RCK domains form a stable octamer in solution, supporting the notion that the formation of octameric gating ring is a functionally relevant event in MthK gating. Additionally, our stability studies indicated that Ca2+ binding stabilizes the RCK domains in this octameric state.


    Related Citations: 
    • Crystal structure and mechanism of a calcium-gated potassium channel
      Jiang, Y., Lee, A., Chen, J., Cadene, M., Chait, B.T., MacKinnon, R.
      (2002) Nature 417: 515

    Organizational Affiliation

    Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Calcium-gated potassium channel mthKA234Methanothermobacter thermautotrophicusMutation(s): 0 
Gene Names: mthK
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
Protein Feature View
Expand
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.80 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.224 
  • R-Value Observed: 0.226 
  • Space Group: H 3 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 164.88α = 90
b = 164.88β = 90
c = 82.852γ = 120
Software Package:
Software NamePurpose
HKL-2000data collection
SCALEPACKdata scaling
CNSrefinement
HKL-2000data reduction
CNSphasing

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2005-10-25
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance