Structure of acid-sensing ion channel 1 at 1.9 Å resolution and low pH


Acid-sensing ion channels (ASICs) are voltage-independent, proton-activated receptors that belong to the epithelial sodium channel/degenerin family of ion channels and are implicated in perception of pain, ischaemic stroke, mechanosensation, learning and memory. Here we report the low-pH crystal structure of a chicken ASIC1 deletion mutant at 1.9 Å resolution. Each subunit of the chalice-shaped homotrimer is composed of short amino and carboxy termini, two transmembrane helices, a bound chloride ion and a disulphide-rich, multidomain extracellular region enriched in acidic residues and carboxyl-carboxylate pairs within 3 Å, suggesting that at least one carboxyl group bears a proton. Electrophysiological studies on aspartate-to-asparagine mutants confirm that these carboxyl-carboxylate pairs participate in proton sensing. Between the acidic residues and the transmembrane pore lies a disulphide-rich ‘thumb’ domain poised to couple the binding of protons to the opening of the ion channel, thus demonstrating that proton activation involves long-range conformational changes.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Function and structure of chicken ASIC1.
Figure 2: Subunit structure and trimer assembly.
Figure 3: Intersubunit interactions and solvent-filled cavities.
Figure 4: Structure and key residues in the transmembrane domains.
Figure 5: Proton- and chloride-binding sites.
Figure 6: Mechanism of pH-dependent gating.


  1. 1

    Krishtal, O. The ASICs: Signaling molecules? Modulators? Trends Neurosci. 26, 477–483 (2003)

  2. 2

    Lingueglia, E. Acid sensing ion channels in sensory perception. J. Biol. Chem. 282, 17325–17329 (2007)

  3. 3

    Kellenberger, S. & Schild, L. Epithelial sodium channel/degenerin family of ion channels: a variety of functions for a shared structure. Physiol. Rev. 82, 735–767 (2002)

  4. 4

    Krishtal, O. A. & Pidoplichko, V. I. A receptor for protons in the nerve cell membrane. Neuroscience 5, 2325–2327 (1980)

  5. 5

    Waldmann, R., Champigny, G., Bassilana, F., Heurteaux, C. & Lazdunski, M. A proton-gated cation channel involved in acid-sensing. Nature 386, 173–177 (1997)

  6. 6

    O’Hagan, R. & Chalfie, M. Mechanosensation in Caenorhabditis elegans. Int. Rev. Neurobiol. 69, 169–203 (2006)

  7. 7

    Lingueglia, E., Deval, E. & Lazdunski, M. FMRFamide-gated sodium channel and ASIC channels: a new class of ionotropic receptors for FMRF-amide and related peptides. Peptides 27, 1138–1152 (2006)

  8. 8

    Chen, C. C., England, S., Akopian, A. N. & Wood, J. N. A sensory neuron-specific, proton-gated ion channel. Proc. Natl Acad. Sci. USA 95, 10240–10245 (1998)

  9. 9

    Price, M. P., Snyder, P. M. & Welsh, M. J. Cloning and expression of a novel human brain Na+ channel. J. Biol. Chem. 271, 7879–7882 (1996)

  10. 10

    Lingueglia, E. et al. A modulatory subunit of acid sensing ion channels in brain and dorsal root ganglion cells. J. Biol. Chem. 272, 29778–29783 (1997)

  11. 11

    Waldmann, R. et al. Molecular cloning of a non-inactivating proton-gated Na+ channel specific for sensory neurons. J. Biol. Chem. 272, 20975–20978 (1997)

  12. 12

    Grunder, S., Geisler, H. S., Bassler, E. L. & Ruppersberg, J. P. A new member of acid-sensing ion channels from pituitary gland. Neuroreport 11, 1607–1611 (2000)

  13. 13

    Alvarez de la Rosa, D., Zhang, P., Shao, D., White, F. & Canessa, C. M. Functional implications of the localization and activity of acid-sensing channels in rat peripheral nervous system. Proc. Natl Acad. Sci. USA 99, 2326–2331 (2002)

  14. 14

    Alvarez de la Rosa, D. et al. Distribution, subcellular localization and ontogeny of ASIC1 in the mammalian central nervous system. J. Physiol. (Lond.) 546, 77–87 (2003)

  15. 15

    Price, M. P. et al. The DRASIC cation channel contributes to the detection of cutaneous touch and acid stimuli in mice. Neuron 32, 1071–1083 (2001)

  16. 16

    Bassilana, F. et al. The acid-sensitive ionic channel subunit ASIC and the mammalian degenerin MDEG form a heteromultimeric H+-gated Na+ channel with novel properties. J. Biol. Chem. 272, 28819–28822 (1997)

  17. 17

    Benson, C. J. et al. Heteromultimers of DEG/ENaC subunits form H+-gated channels in mouse sensory neurons. Proc. Natl Acad. Sci. USA 99, 2338–2343 (2002)

  18. 18

    Wemmie, J. A. et al. The acid-activated ion channel ASIC contributes to synaptic plasticity, learning and memory. Neuron 34, 463–477 (2002)

  19. 19

    Sutherland, S. P., Benson, C. J., Adelman, J. & McCleskey, E. W. Acid-sensing ion channel 3 matches the acid-gated current in cardiac ischemia-sensing neurons. Proc. Natl Acad. Sci. USA 98, 711–716 (2001)

  20. 20

    Xiong, Z. G. et al. Neuroprotection in ischemia: blocking calcium-permeable acid-sensing ion channels. Cell 118, 687–698 (2004)

  21. 21

    Hesselager, M., Timmermann, D. B. & Ahring, P. K. pH dependency and desensitization kinetics of heterologously expressed combinations of acid-sensing ion channel subunits. J. Biol. Chem. 279, 11006–11015 (2004)

  22. 22

    Korkushco, A. O., Krishtal, O. A. & Nowycky, M. C. Steady-state characteristics of the proton receptor in the somatic membrane of rat sensory neurons. Neurofiziologiya 15, 632–638 (1983)

  23. 23

    Immke, D. C. & McCleskey, E. W. Protons open acid-sensing ion channels by catalyzing relief of Ca2+ block. Neuron 37, 75–84 (2003)

  24. 24

    Zhang, P., Sigworth, F. J. & Canessa, C. M. Gating of acid-sensitive ion channel-1: Release of Ca2+ block vs allosteric mechanism. J. Gen. Physiol. 127, 109–117 (2006)

  25. 25

    Baron, A., Waldmann, R. & Lazdunski, M. ASIC-like, proton-activated currents in rat hippocampal neurons. J. Physiol. (Lond.) 539, 485–494 (2002)

  26. 26

    Askwith, C. C., Wemmie, J. A., Price, M. P., Rokhlina, T. & Welsh, M. J. Acid-sensing ion channel 2 (ASIC2) modulates ASIC1 H+-activated currents in hippocampal neurons. J. Biol. Chem. 279, 18296–18305 (2004)

  27. 27

    Coscoy, S., Lingueglia, E., Lazdunski, M. & Barbry, P. The Phe-Met-Arg-Phe-amide-activated sodium channel is a tetramer. J. Biol. Chem. 273, 8317–8322 (1998)

  28. 28

    Snyder, P. M., Cheng, C., Prince, L. S., Rogers, J. C. & Welsh, M. J. Electrophysiological and biochemical evidence that DEG/ENaC cation channels are composed of nine subunits. J. Biol. Chem. 273, 681–684 (1998)

  29. 29

    Coric, T., Zheng, D., Gerstein, M. & Canessa, C. M. Proton sensitivity of ASIC1 appeared with the rise of fishes by changes of residues in the region that follows TM1 in the ectodomain of the channel. J. Physiol. (Lond.) 568, 725–735 (2005)

  30. 30

    Kawate, T. & Gouaux, E. Fluorescence-detection size-exclusion chromatography for precrystallization screening of integral membrane proteins. Structure 14, 673–681 (2006)

  31. 31

    Staruschenko, A., Adams, E., Booth, R. E. & Stockand, J. D. Epithelial Na+ channel subunit stoichiometry. Biophys. J. 88, 3966–3975 (2005)

  32. 32

    Firsov, D., Gautschi, I., Merillat, A.-M., Rossier, B. C. & Schild, L. The heterotetrameric architecture of the epithelial sodium channel (ENaC). EMBO J. 17, 344–352 (1998)

  33. 33

    Eskandari, S. et al. Number of subunits comprising the epithelial sodium channel. J. Biol. Chem. 274, 27281–27286 (1999)

  34. 34

    Unwin, N. Refined structure of the nicotinic acetylcholine receptor. J. Mol. Biol. 346, 967–989 (2005)

  35. 35

    Cushman, K. A., Marsh-Haffner, J., Adelman, J. & McCleskey, E. W. A conformational change in the extracellular domain that accompanies desensitization of acid-sensing ion channel (ASIC) 3. J. Gen. Physiol. 129, 345–350 (2007)

  36. 36

    Coric, T., Zhang, P., Todorovic, N. & Canessa, C. M. The extracellular domain determines the kinetics of desensitization in acid-sensitive ion channel 1. J. Biol. Chem. 278, 45240–45247 (2003)

  37. 37

    Baron, A., Schaefer, L., Lingueglia, E., Champigny, G. & Lazdunski, M. Zn2+ and H+ are coactivators of acid-sensing ion channels. J. Biol. Chem. 276, 35361–35367 (2001)

  38. 38

    Rosenmund, C., Stern-Bach, Y. & Stevens, C. F. The tetrameric structure of a glutamate receptor channel. Science 280, 1596–1599 (1998)

  39. 39

    MacKinnon, R. Determination of the subunit stoichiometry of a voltage-activated potassium channel. Nature 350, 232–235 (1991)

  40. 40

    Reynolds, J. A. & Karlin, A. Molecular weight in detergent solution of acetylcholine receptor from Torpedo californica. Biochemistry 17, 2035–2038 (1978)

  41. 41

    Paukert, M., Babini, E., Pusch, M. & Grunder, S. Identification of the Ca2+ blocking site of acid-sensing ion channel (ASIC) 1: Implications for channel gating. J. Gen. Physiol. 124, 383–394 (2004)

  42. 42

    Kellenberger, S., Auberson, M., Gautschi, I., Schneeberger, E. & Schild, L. Permeability properties of ENaC selectivity filter mutants. J. Gen. Physiol. 118, 679–692 (2001)

  43. 43

    Doyle, D. A. et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280, 69–77 (1998)

  44. 44

    Pfister, Y. et al. A gating mutation in the internal pore of ASIC1a. J. Biol. Chem. 281, 11787–11791 (2006)

  45. 45

    Goodman, M. B. et al. MEC-2 regulates C. elegans DEG/ENaC channels needed for mechanosensation. Nature 415, 1039–1042 (2002)

  46. 46

    Sawyer, L. & James, M. N. Carboxyl-carboxylate interactions in proteins. Nature 295, 79–80 (1982)

  47. 47

    Todorovic, N., Coric, T., Zhang, P. & Canessa, C. M. Effects of extracellular calcium on fASIC1 currents. Ann. NY Acad. Sci. 1048, 331–336 (2005)

  48. 48

    Bellizzi, J. J., Widom, J., Kemp, C. W. & Clardy, J. Producing selenomethionine-labeled proteins with a baculovirus expression vector system. Structure 7, R263–R267 (1999)

  49. 49

    Terwilliger, T. C. & Berendzen, J. Automated MAD and MIR structure solution. Acta Crystallogr. D 55, 849–861 (1999)

  50. 50

    Cowtan, K. & Zhang, K. Y. Density modification for macromolecular phase improvement. Prog. Biophys. Mol. Biol. 72, 245–270 (1999)

  51. 51

    Perrakis, A., Morris, R. & Lamzin, V. S. Automated protein model building combined with iterative structure refinement. Nature Struct. Biol. 6, 458–463 (1999)

  52. 52

    Jones, T. A., Zou, J.-Y. & Cowan, S. W. Improved methods for building protein models in electron density maps and the location of errors in these models. Acta Crystallogr. A 47, 110–119 (1991)

  53. 53

    Brunger, A. T. et al. Crystallography and NMR system: A new software suite for macromolecular structure determination. Acta Crystallogr. D 54, 905–921 (1998)

Download references


We thank all groups that provided us with ASIC DNAs. We thank T. Kawate for sharing the FSEC screening protocol, Gouaux laboratory members and E. McCleskey for discussions. We also thank the personnel at beamlines 8.2.1 and 8.2.2 of the Advanced Light Source and beamline X29 of the National Synchrotron Light Source. This work was supported by the NIH. E.G. is an investigator with the Howard Hughes Medical Institute.

Author Contributions E.G. and J.J. designed the project. J.J. performed cloning, cell culture, FSEC screening, purification and crystallography work. H.F. and E.B.G. did patch-clamp recordings. E.G. and J.J. wrote the manuscript.

Coordinates have been deposited with the Protein Data Bank under code 2QTS.

Author information



Corresponding author

Correspondence to Eric Gouaux.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Information

The file contains Supplementary Table S1, and Supplementary Figures S1-S9 with Legends. (PDF 1209 kb)

Supplementary Movie

This file contains a Supplementary Movie showing speculative mechanism of pH mediated channel gating. Simple animation of domain movement that might occur upon transition from high pH (resting state) to low pH (activated state/desensitized state). At high pH, the finger and thumb domains are separated, perhaps with one or more intervening calcium ions binding in the interdomain cleft and the ion channel is in closed state. Upon exposure to low pH, the calcium ions are released, the key acidic residues bind protons, the thumb and finger domains move closer, pivoting around the β-ball domain, and the ion channel opens and then desensitizes, coupled to the thumb domain by way of the ball-and-socket joint at the wrist junction. This file was uploaded on 11 October 2007 and the legend updated on 18 October 2007. (HTML 1105 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Jasti, J., Furukawa, H., Gonzales, E. et al. Structure of acid-sensing ion channel 1 at 1.9 Å resolution and low pH. Nature 449, 316–323 (2007).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.