4WFG

Human TRAAK K+ channel in a Tl+ bound conductive conformation


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.202 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Physical mechanism for gating and mechanosensitivity of the human TRAAK K+ channel.

Brohawn, S.G.Campbell, E.B.MacKinnon, R.

(2014) Nature 516: 126-130

  • DOI: 10.1038/nature14013
  • Primary Citation of Related Structures:  4WFE, 4WFF, 4WFH

  • PubMed Abstract: 
  • Activation of mechanosensitive ion channels by physical force underlies many physiological processes including the sensation of touch, hearing and pain. TRAAK (also known as KCNK4) ion channels are neuronally expressed members of the two-pore domain ...

    Activation of mechanosensitive ion channels by physical force underlies many physiological processes including the sensation of touch, hearing and pain. TRAAK (also known as KCNK4) ion channels are neuronally expressed members of the two-pore domain K(+) (K2P) channel family and are mechanosensitive. They are involved in controlling mechanical and temperature nociception in mice. Mechanosensitivity of TRAAK is mediated directly through the lipid bilayer--it is a membrane-tension-gated channel. However, the molecular mechanism of TRAAK channel gating and mechanosensitivity is unknown. Here we present crystal structures of TRAAK in conductive and non-conductive conformations defined by the presence of permeant ions along the conduction pathway. In the non-conductive state, a lipid acyl chain accesses the channel cavity through a 5 Å-wide lateral opening in the membrane inner leaflet and physically blocks ion passage. In the conductive state, rotation of a transmembrane helix (TM4) about a central hinge seals the intramembrane opening, preventing lipid block of the cavity and permitting ion entry. Additional rotation of a membrane interacting TM2-TM3 segment, unique to mechanosensitive K2Ps, against TM4 may further stabilize the conductive conformation. Comparison of the structures reveals a biophysical explanation for TRAAK mechanosensitivity--an expansion in cross-sectional area up to 2.7 nm(2) in the conductive state is expected to create a membrane-tension-dependent energy difference between conformations that promotes force activation. Our results show how tension of the lipid bilayer can be harnessed to control gating and mechanosensitivity of a eukaryotic ion channel.


    Organizational Affiliation

    Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Potassium channel subfamily K member 4
A, B
299Homo sapiensGene Names: KCNK4 (TRAAK)
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
Channels: Potassium, Sodium, & Proton Ion-Selective
Protein: 
Two-Pore Domain Potassium Channel K2P4.1 (TRAAK)
Find proteins for Q9NYG8 (Homo sapiens)
Go to Gene View: KCNK4
Go to UniProtKB:  Q9NYG8
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
ANTI-TRAAK ANTIBODY 13E9 FAB FRAGMENT LIGHT CHAIN
D, F
211N/AN/A
Protein Feature View is not available: No corresponding UniProt sequence found.
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
ANTI-TRAAK ANTIBODY 13E9 FAB FRAGMENT HEAVY CHAIN
E, G
217N/AN/A
Protein Feature View is not available: No corresponding UniProt sequence found.
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

Download SDF File 
Download CCD File 
A, G
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
TL
Query on TL

Download SDF File 
Download CCD File 
A, B
THALLIUM (I) ION
Tl
ZLUSCZLCHQSJRU-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.202 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 80.798α = 90.00
b = 138.760β = 94.52
c = 96.317γ = 90.00
Software Package:
Software NamePurpose
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2014-12-03
    Type: Initial release
  • Version 1.1: 2014-12-17
    Type: Database references