4GOW

Crystal Structure of Ca2+/CaM:Kv7.4 (KCNQ4) B helix complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.268 
  • R-Value Work: 0.236 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Structure of a Ca(2+)/CaM:Kv7.4 (KCNQ4) B-helix complex provides insight into M current modulation.

Xu, Q.Chang, A.Tolia, A.Minor, D.L.

(2013) J.Mol.Biol. 425: 378-394

  • DOI: 10.1016/j.jmb.2012.11.023

  • PubMed Abstract: 
  • Calmodulin (CaM) is an important regulator of Kv7.x (KCNQx) voltage-gated potassium channels. Channels from this family produce neuronal M currents and cardiac and auditory I(KS) currents and harbor mutations that cause arrhythmias, epilepsy, and dea ...

    Calmodulin (CaM) is an important regulator of Kv7.x (KCNQx) voltage-gated potassium channels. Channels from this family produce neuronal M currents and cardiac and auditory I(KS) currents and harbor mutations that cause arrhythmias, epilepsy, and deafness. Despite extensive functional characterization, biochemical and structural details of the interaction between CaM and the channel have remained elusive. Here, we show that both apo-CaM and Ca(2+)/CaM bind to the C-terminal tail of the neuronal channel Kv7.4 (KCNQ4), which is involved in both hearing and mechanosensation. Interactions between apo-CaM and the Kv7.4 tail involve two C-terminal tail segments, known as the A and B segments, whereas the interaction between Ca(2+)/CaM and the Kv7.4 C-terminal tail requires only the B segment. Biochemical studies show that the calcium dependence of the CaM:B segment interaction is conserved in all Kv7 subtypes. X-ray crystallographic determination of the structure of the Ca(2+)/CaM:Kv7.4 B segment complex shows that Ca(2+)/CaM wraps around the Kv7.4 B segment, which forms an α-helix, in an antiparallel orientation that embodies a variation of the classic 1-14 Ca(2+)/CaM interaction motif. Taken together with the context of prior studies, our data suggest a model for modulation of neuronal Kv7 channels involving a calcium-dependent conformational switch from an apo-CaM form that bridges the A and B segments to a Ca(2+)/CaM form bound to the B-helix. The structure presented here also provides a context for a number of disease-causing mutations and for further dissection of the mechanisms by which CaM controls Kv7 function.


    Organizational Affiliation

    Cardiovascular Research Institute, University of California, San Francisco, CA 94158-2156, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Calmodulin
D
144Homo sapiensMutation(s): 0 
Gene Names: CALM1 (CALM, CAM, CAM1)
Find proteins for P0DP23 (Homo sapiens)
Go to Gene View: CALM1
Go to UniProtKB:  P0DP23
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Potassium voltage-gated channel subfamily KQT member 4
A
72Homo sapiensMutation(s): 0 
Gene Names: KCNQ4
Find proteins for P56696 (Homo sapiens)
Go to Gene View: KCNQ4
Go to UniProtKB:  P56696
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

Download SDF File 
Download CCD File 
D
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.268 
  • R-Value Work: 0.236 
  • Space Group: P 65 2 2
Unit Cell:
Length (Å)Angle (°)
a = 104.075α = 90.00
b = 104.075β = 90.00
c = 113.729γ = 120.00
Software Package:
Software NamePurpose
MOSFLMdata reduction
PHENIXrefinement
PHASERphasing
PDB_EXTRACTdata extraction
HKL-2000data collection
SCALAdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2012-12-12
    Type: Initial release
  • Version 1.1: 2013-05-22
    Type: Database references