5OYB

Structure of calcium-bound mTMEM16A chloride channel at 3.75 A resolution


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.75 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Activation mechanism of the calcium-activated chloride channel TMEM16A revealed by cryo-EM.

Paulino, C.Kalienkova, V.Lam, A.K.M.Neldner, Y.Dutzler, R.

(2017) Nature 552: 421-425

  • DOI: 10.1038/nature24652
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The calcium-activated chloride channel TMEM16A is a ligand-gated anion channel that opens in response to an increase in intracellular Ca2+ concentration. The protein is broadly expressed and contributes to diverse physiological processes, including t ...

    The calcium-activated chloride channel TMEM16A is a ligand-gated anion channel that opens in response to an increase in intracellular Ca2+ concentration. The protein is broadly expressed and contributes to diverse physiological processes, including transepithelial chloride transport and the control of electrical signalling in smooth muscles and certain neurons. As a member of the TMEM16 (or anoctamin) family of membrane proteins, TMEM16A is closely related to paralogues that function as scramblases, which facilitate the bidirectional movement of lipids across membranes. The unusual functional diversity of the TMEM16 family and the relationship between two seemingly incompatible transport mechanisms has been the focus of recent investigations. Previous breakthroughs were obtained from the X-ray structure of the lipid scramblase of the fungus Nectria haematococca (nhTMEM16), and from the cryo-electron microscopy structure of mouse TMEM16A at 6.6 Å (ref. 14). Although the latter structure disclosed the architectural differences that distinguish ion channels from lipid scramblases, its low resolution did not permit a detailed molecular description of the protein or provide any insight into its activation by Ca2+. Here we describe the structures of mouse TMEM16A at high resolution in the presence and absence of Ca2+. These structures reveal the differences between ligand-bound and ligand-free states of a calcium-activated chloride channel, and when combined with functional experiments suggest a mechanism for gating. During activation, the binding of Ca2+ to a site located within the transmembrane domain, in the vicinity of the pore, alters the electrostatic properties of the ion conduction path and triggers a conformational rearrangement of an α-helix that comes into physical contact with the bound ligand, and thereby directly couples ligand binding and pore opening. Our study describes a process that is unique among channel proteins, but one that is presumably general for both functional branches of the TMEM16 family.


    Organizational Affiliation

    Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Anoctamin-1
A, B
960Mus musculusMutation(s): 0 
Gene Names: Ano1 (Tmem16a)
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
TMEM16 Family Proteins
Protein: 
TMEM16A calcium-activated chloride channel
Find proteins for Q8BHY3 (Mus musculus)
Go to UniProtKB:  Q8BHY3
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

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

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.75 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 
Software Package:
Software NamePurpose
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
University of ZurichSwitzerlandFK-16-036
European Research CouncilSwitzerland339116AnoBest

Revision History 

  • Version 1.0: 2017-12-20
    Type: Initial release
  • Version 1.1: 2017-12-27
    Type: Database references
  • Version 1.2: 2018-01-10
    Type: Database references
  • Version 1.3: 2018-10-17
    Type: Author supporting evidence, Data collection