Diamond-shaped octameric ring structure of an RCK domain with ATP bound

Experimental Data Snapshot

  • Resolution: 2.25 Å
  • R-Value Free: 0.245 
  • R-Value Work: 0.228 

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This is version 1.5 of the entry. See complete history


The RCK Domain of the KtrAB K(+) Transporter: Multiple Conformations of an Octameric Ring.

Albright, R.A.Ibar, J.L.Kim, C.U.Gruner, S.M.Morais-Cabral, J.H.

(2006) Cell 126: 1147-1159

  • DOI: https://doi.org/10.1016/j.cell.2006.08.028
  • Primary Citation of Related Structures:  
    2HMS, 2HMT, 2HMU, 2HMV, 2HMW

  • PubMed Abstract: 

    The KtrAB ion transporter is a complex of the KtrB membrane protein and KtrA, an RCK domain. RCK domains regulate eukaryotic and prokaryotic membrane proteins involved in K(+) transport. Conflicting functional models have proposed two different oligomeric arrangements for RCK domains, tetramer versus octamer. Our results for the KtrAB RCK domain clearly show an octamer in solution and in the crystal. We determined the structure of this protein in three different octameric ring conformations that resemble the RCK-domain octamer observed in the MthK potassium channel but show striking differences in size and symmetry. We present experimental evidence for the association between one RCK octameric ring and two KtrB membrane proteins. These results provide insights into the quaternary organization of the KtrAB transporter and its mechanism of activation and show that the RCK-domain octameric ring model is generally applicable to other ion-transport systems.

  • Organizational Affiliation

    Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
YuaA protein
A, B
144Bacillus subtilisMutation(s): 1 
Gene Names: yuaA
Find proteins for O32080 (Bacillus subtilis (strain 168))
Explore O32080 
Go to UniProtKB:  O32080
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO32080
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on ATP

Download Ideal Coordinates CCD File 
C [auth A],
D [auth B]
C10 H16 N5 O13 P3
Binding Affinity Annotations 
IDSourceBinding Affinity
ATP PDBBind:  2HMU Kd: 20 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.25 Å
  • R-Value Free: 0.245 
  • R-Value Work: 0.228 
  • Space Group: P 4 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 127.668α = 90
b = 127.668β = 90
c = 51.88γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2006-09-26
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-18
    Changes: Refinement description
  • Version 1.4: 2021-10-20
    Changes: Database references, Derived calculations
  • Version 1.5: 2023-08-30
    Changes: Data collection, Refinement description