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X-ray structure of acid-sensing ion channel 1-snake toxin complex reveals open state of a Na(+)-selective channel

Isabelle Baconguis1, Christopher J Bohlen2, April Goehring1

  • 1Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.

Cell
|February 11, 2014
PubMed

Insights

This study reveals the open state structure of acid-sensing ion channels (ASICs) using MitTx toxin. The findings clarify the selectivity filter’s conformation and ion blockage mechanism in these crucial pain-sensing proteins.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Neuroscience

Background:

  • Acid-sensing ion channels (ASICs) are crucial for detecting extracellular acidity.
  • ASICs are implicated in pain and neurological conditions like ischemic injury.
  • They belong to the degenerin/epithelial sodium channel superfamily.

Purpose of the Study:

  • To determine the cocrystal structure of chicken ASIC1a bound to MitTx.
  • To elucidate the structural basis of the ASIC1a open state.
  • To define the conformation of the ASIC selectivity filter.

Main Methods:

  • Cocrystallization of chicken ASIC1a with MitTx toxin.
  • X-ray crystallography to determine the 3D structure.
  • Structural analysis of the ASIC1a-MitTx complex.

Main Results:

  • The cocrystal structure of chicken ASIC1a in its open state with MitTx was determined.
  • TM2 forms a discontinuous alpha helix in the open and desensitized states.
  • The Gly-Ala-Ser selectivity filter adopts an extended, belt-like conformation, blocking hydrated ions.

Conclusions:

  • The structure captures the open state of ASIC1a, providing insights into channel gating.
  • The findings illuminate the mechanism of MitTx action on ASICs.
  • This work defines the selectivity filter structure of voltage-independent, sodium-selective ion channels.

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