6N5W

Crystal structure of the Ca2+/CaM complex with independent peptides of Kv7.4 (KCNQ4) A & B domains


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.15 Å
  • R-Value Free: 0.274 
  • R-Value Work: 0.233 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

A mutually induced conformational fit underlies Ca2+-directed interactions between calmodulin and the proximal C terminus of KCNQ4 K+channels.

Archer, C.R.Enslow, B.T.Taylor, A.B.De la Rosa, V.Bhattacharya, A.Shapiro, M.S.

(2019) J. Biol. Chem. 294: 6094-6112

  • DOI: 10.1074/jbc.RA118.006857

  • PubMed Abstract: 
  • Calmodulin (CaM) conveys intracellular Ca <sup>2+ </sup> signals to KCNQ (Kv7, "M-type") K <sup>+ </sup> channels and many other ion channels. Whether this "calmodulation" involves a dramatic structural rearrangement or only slight perturbations of t ...

    Calmodulin (CaM) conveys intracellular Ca 2+ signals to KCNQ (Kv7, "M-type") K + channels and many other ion channels. Whether this "calmodulation" involves a dramatic structural rearrangement or only slight perturbations of the CaM/KCNQ complex is as yet unclear. A consensus structural model of conformational shifts occurring between low nanomolar and physiologically high intracellular [Ca 2+ ] is still under debate. Here, we used various techniques of biophysical chemical analyses to investigate the interactions between CaM and synthetic peptides corresponding to the A and B domains of the KCNQ4 subtype. We found that in the absence of CaM, the peptides are disordered, whereas Ca 2+ /CaM imposed helical structure on both KCNQ A and B domains. Isothermal titration calorimetry revealed that Ca 2+ /CaM has higher affinity for the B domain than for the A domain of KCNQ2-4 and much higher affinity for the B domain when prebound with the A domain. X-ray crystallography confirmed that these discrete peptides spontaneously form a complex with Ca 2+ /CaM, similar to previous reports of CaM binding KCNQ-AB domains that are linked together. Microscale thermophoresis and heteronuclear single-quantum coherence NMR spectroscopy indicated the C-lobe of Ca 2+ -free CaM to interact with the KCNQ4 B domain ( K d ∼10-20 μm), with increasing Ca 2+ molar ratios shifting the CaM-B domain interactions via only the CaM C-lobe to also include the N-lobe. Our findings suggest that in response to increased Ca 2+ , CaM undergoes lobe switching that imposes a dramatic mutually induced conformational fit to both the proximal C terminus of KCNQ4 channels and CaM, likely underlying Ca 2+ -dependent regulation of KCNQ gating.


    Organizational Affiliation

    Biochemistry and Structural Biology and.,the Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas 78229.,From the Departments of Cell and Integrative Physiology and shapirom@uthscsa.edu.,From the Departments of Cell and Integrative Physiology and.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Potassium voltage-gated channel subfamily KQT member 4
A
27Homo sapiensMutation(s): 0 
Gene Names: KCNQ4
Find proteins for P56696 (Homo sapiens)
Go to Gene View: KCNQ4
Go to UniProtKB:  P56696
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Potassium voltage-gated channel subfamily KQT member 4
B
26Homo sapiensMutation(s): 0 
Gene Names: KCNQ4
Find proteins for P56696 (Homo sapiens)
Go to Gene View: KCNQ4
Go to UniProtKB:  P56696
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
Calmodulin-1
C
149Homo sapiensMutation(s): 0 
Gene Names: CALM1 (CALM, CAM, CAM1)
Find proteins for P0DP23 (Homo sapiens)
Go to Gene View: CALM1
Go to UniProtKB:  P0DP23
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

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

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.15 Å
  • R-Value Free: 0.274 
  • R-Value Work: 0.233 
  • Space Group: P 21 21 2
Unit Cell:
Length (Å)Angle (°)
a = 43.510α = 90.00
b = 130.570β = 90.00
c = 36.160γ = 90.00
Software Package:
Software NamePurpose
XDSdata scaling
PHENIXrefinement
PHASERphasing
XDSdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of Neurological Disorders and StrokeUnited StatesR01 NS043394
National Institutes of Health/National Institute of Neurological Disorders and StrokeUnited StatesR01 NS094461
National Institutes of Health/National Heart, Lung, and Blood InstituteUnited StatesT32 HL007446

Revision History 

  • Version 1.0: 2019-03-13
    Type: Initial release
  • Version 1.1: 2019-04-24
    Type: Data collection, Database references