Biological Assembly 1  

 3D View: Structure | Electron Density

Global Symmetry: Cyclic - C4  (3D View)
Global Stoichiometry: Homo 4-mer - A4 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 89.37 kDa 
• Atom Count: 5076 
• Residue Count: 648 
• Unique protein chains: 1

3NAF

Structure of the Intracellular Gating Ring from the Human High-conductance Ca2+ gated K+ Channel (BK Channel)

• DOI: 10.2210/pdb3NAF/pdb

• Classification: ION TRANSPORT
• Organism(s): Homo sapiens
• Expression System: Spodoptera frugiperda
• Mutation(s): No 


• Deposited: 2010-06-01 Released: 2010-06-30 
• Deposition Author(s): Wu, Y., Yang, Y., Ye, S., Jiang, Y.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 3.10 Å
• R-Value Free: 0.289 
• R-Value Work: 0.238 
• R-Value Observed: 0.243 

Literature

Structure of the gating ring from the human large-conductance Ca(2+)-gated K(+) channel.

Wu, Y., Yang, Y., Ye, S., Jiang, Y.

(2010) Nature 466: 393-397

• PubMed: 20574420 
• DOI: 10.1038/nature09252
• Primary Citation of Related Structures:  
  3NAF


• PubMed Abstract: 
  

Large-conductance Ca(2+)-gated K(+) (BK) channels are essential for many biological processes such as smooth muscle contraction and neurotransmitter release. This group of channels can be activated synergistically by both voltage and intracellular Ca(2+), with the large carboxy-terminal intracellular portion being responsible for Ca(2+) sensing. Here we present the crystal structure of the entire cytoplasmic region of the human BK channel in a Ca(2+)-free state. The structure reveals four intracellular subunits, each comprising two tandem RCK domains, assembled into a gating ring similar to that seen in the MthK channel and probably representing its physiological assembly. Three Ca(2+) binding sites including the Ca(2+) bowl are mapped onto the structure based on mutagenesis data. The Ca(2+) bowl, located within the second RCK domain, forms an EF-hand-like motif and is strategically positioned close to the assembly interface between two subunits. The other two Ca(2+) (or Mg(2+)) binding sites, Asp 367 and Glu 374/Glu 399, are located on the first RCK domain. The Asp 367 site has high Ca(2+) sensitivity and is positioned in the groove between the amino- and carboxy-terminal subdomains of RCK1, whereas the low-affinity Mg(2+)-binding Glu 374/Glu 399 site is positioned on the upper plateau of the gating ring and close to the membrane. Our structure also contains the linker connecting the transmembrane and intracellular domains, allowing us to dock a voltage-gated K(+) channel pore of known structure onto the gating ring with reasonable accuracy and generate a structural model for the full BK channel.

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Organizational Affiliation: 

Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Calcium-activated potassium channel subunit alpha-1,Calcium-activated potassium channel subunit alpha-1,Calcium-activated potassium channel subunit alpha-1	A	798	Homo sapiens	Mutation(s): 0  Gene Names: KCNMA1, KCNMA, SLO
Membrane protein Mpstruc	Group:  TRANSMEMBRANE PROTEINS: ALPHA-HELICAL		Sub Group:  Channels: Potassium, Sodium, & Proton Ion-Selective	Protein:  Human BK (SLO1) Channel Ca2+-activation apparatus
Find proteins for Q12791 (Homo sapiens) Explore Q12791  Go to UniProtKB:  Q12791
NIH Common Fund Data Resources
PHAROS:  Q12791 GTEx:  ENSG00000156113

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 3.10 Å
• R-Value Free: 0.289 
• R-Value Work: 0.238 
• R-Value Observed: 0.243 
• Space Group: I 4 2 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 134.395	α = 90
b = 134.395	β = 90
c = 231.84	γ = 90

Software Package:

Software Name	Purpose
HKL-2000	data collection
SHARP	phasing
PHENIX	refinement
HKL-2000	data reduction
HKL-2000	data scaling

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2010-06-01 
• Released Date: 2010-06-30 
Deposition Author(s): Wu, Y., Yang, Y., Ye, S., Jiang, Y.

Revision History 

• Version 1.0: 2010-06-30
  Type: Initial release
  
• Version 1.1: 2011-07-13
  Changes: Version format compliance
• Version 1.2: 2014-11-12
  Changes: Structure summary
• Version 1.3: 2017-06-21
  Changes: Database references, Source and taxonomy, Structure summary