Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Review Article
  • Published:

Ion channel structure

Emerging structure of the Nicotinic Acetylcholine receptors

Nature Reviews Neuroscience volume 3, pages 102–114 (2002)Cite this article

Key Points

  • Nicotinic acetylcholine (ACh) receptors and other Cys-loop receptors challenge our ability to understand how proteins carry out simple sets of functions — in this case, specific binding, conversion of binding into channel opening, selective conduction, and desensitization.

  • The crystal structure of an ACh-binding protein that is homologous to the extracellular domain of the receptors has provided a detailed framework for interpreting the results of decades of biochemical work. The ACh-binding sites have been definitively located between subunits, with adjacent subunits contributing crucial residues.

  • A crystal structure of α-bungarotoxin bound to a synthetic peptide that mimics a binding-site loop of the ACh-binding protein has revealed the mode of binding of snake α-neurotoxins to the ACh receptors.

  • The structure of the channel lining, which is formed by the membrane-spanning segments of each of the five receptor subunits, has been inferred from photolabelling, mutagenesis, a combination of mutagenesis and chemical probing, and electron microscopy.

  • All of these approaches have provided evidence that extensive conformational changes accompany shifts of the receptor from one functional state to another.

  • Key among the changes are the opening and closing of gates, which are detected most sensitively by electrophysiological means. Inferences that have been made about the nature and location of these gates are not all in agreement.

  • The residues that determine the selectivity of the channel for the charge and size of permeating ions have been identified, but understanding the physical basis of their roles is likely to require a high-resolution structure of the protein.

Abstract

The conversion of acetylcholine binding into ion conduction across the membrane is becoming more clearly understood in terms of the structure of the receptor and its transitions. A high-resolution structure of a protein that is homologous to the extracellular domain of the receptor has revealed the binding sites and subunit interfaces in great detail. Although the structures of the membrane and cytoplasmic domains are less well determined, the channel lining and the determinants of selectivity have been mapped. The location and structure of the gates, and the coupling between binding sites and gates, remain to be established.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Structure of the nicotinic acetylcholine receptors.
Figure 2: Transitions between the four states of the ACh receptor.
Figure 3: The acetylcholine-binding protein.
Figure 4: Aligned sequences of the extracellular domains of the Torpedo californica ACh receptor α-, γ-, and δ-subunits.
Figure 5: The binding site of AChBP.
Figure 6: M1, M2 and the M1–M2 loop of the mouse muscle ACh receptor.

Similar content being viewed by others

References

  1. Langley, J. N. On the contraction of muscle chiefly in relation to the presence of receptive substances. Part 1. J. Physiol. (Lond.) 36, 347–384 (1907).

    Article  CAS  Google Scholar 

  2. Katz, B. & Thesleff, S. A study of 'desensitization' produced by acetylcholine at the motor end-plate. J. Physiol. (Lond.) 138, 63–80 (1957).

    Article  CAS  Google Scholar 

  3. Kao, P. N. & Karlin, A. Acetylcholine receptor binding site contains a disulfide cross-link between adjacent half-cystinyl residues. J. Biol. Chem. 261, 8085–8088 (1986).

    CAS  PubMed  Google Scholar 

  4. Karlin, A. & Akabas, M. H. Toward a structural basis for the function of nicotinic acetylcholine receptors and their cousins. Neuron 15, 1231–1244 (1995).

    Article  CAS  PubMed  Google Scholar 

  5. Ortells, M. O. & Lunt, G. G. Evolutionary history of the ligand-gated ion-channel superfamily of receptors. Trends Neurosci. 18, 121–127 (1995).

    Article  CAS  PubMed  Google Scholar 

  6. Tsunoyama, K. & Gojobori, T. Evolution of nicotinic acetylcholine receptor subunits. Mol. Biol. Evol. 15, 518–527 (1998).

    Article  CAS  PubMed  Google Scholar 

  7. Cully, D. F. et al. Cloning an avermectin-sensitive glutamate-gated chloride channel from Caenorhabditis elegans. Nature 371, 707–711 (1994).

    Article  CAS  PubMed  Google Scholar 

  8. Zheng, Y. et al. Identification of two novel Drosophila melanogaster histamine-gated chloride channel subunits expressed in the eye. J. Biol. Chem. 277, 2000–2005 (2002).

    Article  CAS  PubMed  Google Scholar 

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

    Article  CAS  PubMed  Google Scholar 

  10. Mishina, M. et al. Molecular distinction between fetal and adult forms of muscle acetylcholine receptor. Nature 321, 406–411 (1986).

    Article  CAS  PubMed  Google Scholar 

  11. Anand, R., Conroy, W. G., Schoepfer, R., Whiting, P. & Lindstrom, J. Neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes have a pentameric quaternary structure. J. Biol. Chem. 266, 11192–11198 (1991).

    CAS  PubMed  Google Scholar 

  12. Cooper, E., Couturier, S. & Ballivet, M. Pentameric structure and subunit stoichiometry of a neuronal nicotinic acetylcholine receptor. Nature 350, 235–238 (1991).

    Article  CAS  PubMed  Google Scholar 

  13. Elgoyhen, A. B., Johnson, D. S., Boulter, J., Vetter, D. E. & Heinemann, S. α9: an acetylcholine receptor with novel pharmacological properties expressed in rat cochlear hair cells. Cell 79, 705–715 (1994).

    Article  CAS  PubMed  Google Scholar 

  14. Gotti, C. et al. Pharmacology and biophysical properties of α7 and α7–α8 α-bungarotoxin receptor subtypes immunopurified from the chick optic lobe. Eur. J. Neurosci. 6, 1281–1291 (1994).

    Article  CAS  PubMed  Google Scholar 

  15. Vernallis, A. B., Conroy, W. G. & Berg, D. K. Neurons assemble acetylcholine receptors with as many as three kinds of subunits while maintaining subunit segregation among receptor subtypes. Neuron 10, 451–464 (1993).

    Article  CAS  PubMed  Google Scholar 

  16. Le Novere, N., Zoli, M. & Changeux, J. P. Neuronal nicotinic receptor α6 subunit mRNA is selectively concentrated in catecholaminergic nuclei of the rat brain. Eur. J. Neurosci. 8, 2428–2439 (1996).

    Article  CAS  PubMed  Google Scholar 

  17. Ramirez-Latorre, J. et al. Functional contributions of α5 subunit to neuronal acetylcholine receptor channels. Nature 380, 347–351 (1996).

    Article  CAS  PubMed  Google Scholar 

  18. Elgoyhen, A. B. et al. α10: a determinant of nicotinic cholinergic receptor function in mammalian vestibular and cochlear mechanosensory hair cells. Proc. Natl Acad. Sci. USA 98, 3501–3506 (2001).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Karlin, A. et al. The arrangement of the subunits of the acetylcholine receptor of Torpedo californica. J. Biol. Chem. 258, 6678–6681 (1983).

    CAS  PubMed  Google Scholar 

  20. Stroud, R. M., McCarthy, M. P. & Shuster, M. Nicotinic acetylcholine receptor superfamily of ligand-gated ion channels. Biochemistry 29, 11009–11023 (1990).

    Article  CAS  PubMed  Google Scholar 

  21. Unwin, N. Nicotinic acetylcholine receptor at 9 Å resolution. J. Mol. Biol. 229, 1101–1124 (1993).

    Article  CAS  PubMed  Google Scholar 

  22. Miyazawa, A., Fujiyoshi, Y., Stowell, M. & Unwin, N. Nicotinic acetylcholine receptor at 4.6 Å resolution: transverse tunnels in the channel wall. J. Mol. Biol. 288, 765–786 (1999).

    Article  CAS  PubMed  Google Scholar 

  23. Sakmann, B., Patlak, J. & Neher, E. Single acetylcholine-activated channels show burst-kinetics in presence of desensitizing concentrations of agonist. Nature 286, 71–73 (1980).

    Article  CAS  PubMed  Google Scholar 

  24. Neubig, R. R., Boyd, N. D. & Cohen, J. B. Conformations of Torpedo acetylcholine receptor associated with ion transport and desensitization. Biochemistry 21, 3460–3467 (1982).

    Article  CAS  PubMed  Google Scholar 

  25. Heidmann, T., Bernhardt, J., Neumann, E. & Changeux, J. P. Rapid kinetics of agonist-binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata. Biochemistry 22, 5452–5459 (1983).

    Article  CAS  PubMed  Google Scholar 

  26. Jackson, M. B. Perfection of a synaptic receptor: kinetics and energetics of the acetylcholine receptor. Proc. Natl Acad. Sci. USA 86, 2199–2203 (1989).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Auerbach, A. A statistical analysis of acetylcholine receptor activation in Xenopus myocytes: stepwise versus concerted models of gating. J. Physiol. (Lond.) 461, 339–378 (1993).

    Article  CAS  Google Scholar 

  28. Hess, G. Determination of the chemical mechanism of neurotransmitter receptor-mediated reaction by rapid chemical kinetic techniques. Biochemistry 32, 989–1000 (1993).

    Article  CAS  PubMed  Google Scholar 

  29. Edelstein, S. J., Schaad, O., Henry, E., Bertrand, D. & Changeux, J. P. A kinetic mechanism for nicotinic acetylcholine receptors based on multiple allosteric transitions. Biol. Cybern. 75, 361–379 (1996).

    Article  CAS  PubMed  Google Scholar 

  30. Auerbach, A. & Akk, G. Desensitization of mouse nicotinic acetylcholine receptor channels. A two-gate mechanism. J. Gen. Physiol. 112, 181–197 (1998).A thorough single-channel analysis of the fast phase of desensitization finds that the receptor desensitizes most readily from the open state and, as first shown in reference 2 , returns to the resting state without opening. The authors propose an interesting model in which there are separate resting and desensitization gates that are alternately open and closed, the interaction of which determines the kinetics of desensitization and recovery.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  31. Prince, R. J. & Sine, S. M. Acetylcholine and epibatidine binding to muscle acetylcholine receptors distinguish between concerted and uncoupled models. J. Biol. Chem. 274, 19623–19629 (1999).The ACh-binding sites seem to switch independently between functional states, generating asymmetrical states, contrary to the MWC postulate of concerted transitions.

    Article  CAS  PubMed  Google Scholar 

  32. Reitstetter, R., Lukas, R. J. & Gruener, R. Dependence of nicotinic acetylcholine receptor recovery from desensitization on the duration of agonist exposure. J. Pharmacol. Exp. Ther. 289, 656–660 (1999).

    CAS  PubMed  Google Scholar 

  33. Grosman, C. & Auerbach, A. The dissociation of acetylcholine from open nicotinic receptor channels. Proc. Natl Acad. Sci. USA 98, 14102–14107 (2001).This is another searching analysis of receptor kinetics from Auerbach's laboratory, which expands the work of reference 30 . This one estimates the rate constants for the association and dissociation of agonist from the open state, and yields the theoretically expected result that the much higher affinity of agonist for the open state than for the resting state drives activation.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Jones, M. V. & Westbrook, G. L. The impact of receptor desensitization on fast synaptic transmission. Trends Neurosci. 19, 96–101 (1996).

    Article  CAS  PubMed  Google Scholar 

  35. Monod, J., Wyman, J. & Changeux, J.-P. On the nature of allosteric transitions: a plausible model. J. Mol. Biol. 12, 88–118 (1965).

    Article  CAS  PubMed  Google Scholar 

  36. Changeux, J.-P., Thiery, J., Tung, Y. & Kittel, C. On the cooperativity of biological membranes. Proc. Natl Acad. Sci. USA 57, 335–341 (1967).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Karlin, A. On the application of 'a plausible model' of allosteric proteins to the receptor for acetylcholine. J. Theor. Biol. 16, 306–320 (1967).

    Article  CAS  PubMed  Google Scholar 

  38. Kawai, H., Cao, L., Dunn, S. M., Dryden, W. F. & Raftery, M. A. Interaction of a semirigid agonist with Torpedo acetylcholine receptor. Biochemistry 39, 3867–3876 (2000).

    Article  CAS  PubMed  Google Scholar 

  39. Krauss, M., Korr, D., Herrmann, A. & Hucho, F. Binding properties of agonists and antagonists to distinct allosteric states of the nicotinic acetylcholine receptor are incompatible with a concerted model. J. Biol. Chem. 275, 30196–30201 (2000).

    Article  CAS  PubMed  Google Scholar 

  40. Brejc, K. et al. Crystal structure of an ACh-binding protein reveals the ligand-binding domain of nicotinic receptors. Nature 411, 269–276 (2001).The structure of the snail AChBP is solved, illuminating 30 years of research on the ACh receptor and other Cys-loop receptors, and uncovering fascinating details that only a high-resolution structure can provide.

    Article  CAS  PubMed  Google Scholar 

  41. Smit, A. B. et al. A glia-derived acetylcholine-binding protein that modulates synaptic transmission. Nature 411, 261–268 (2001).The discovery and properties of the snail AChBP are described, and evidence is presented that this protein, secreted by snail glia, has an unusual role in shaping neurotransmission by acetylcholine in snail synapses.

    Article  CAS  PubMed  Google Scholar 

  42. Ratnam, M. et al. Location of antigenic determinants on primary sequences of subunits of nicotinic acetylcholine receptor by peptide mapping. Biochemistry 25, 2621–2632 (1986).

    Article  CAS  PubMed  Google Scholar 

  43. Le Novere, N., Corringer, P. J. & Changeux, J. P. Improved secondary structure predictions for a nicotinic receptor subunit: incorporation of solvent accessibility and experimental data into a two-dimensional representation. Biophys. J. 76, 2329–2345 (1999).This paper provides a paradigm for integrating the outputs of several prediction programs to obtain a consensus secondary structure for members of a protein family. Judging by the subsequently solved structure of the homologous AChBP, the prediction was remarkably good.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  44. Karlin, A. Explorations of the nicotinic acetylcholine receptor. Harvey Lect. 85, 71–107 (1991).

    CAS  Google Scholar 

  45. Reiter, M. J., Cowburn, D. A., Prives, J. M. & Karlin, A. Affinity labeling of the acetylcholine receptor in the electroplax: electrophoretic separation in sodium dodecyl sulfate. Proc. Natl Acad. Sci. USA 69, 1168–1172 (1972).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  46. Kao, P. N. et al. Identification of the α subunit half-cystine specifically labeled by an affinity reagent for the acetylcholine receptor binding site. J. Biol. Chem. 259, 11662–11665 (1984).

    CAS  PubMed  Google Scholar 

  47. Galzi, J.-L. et al. Identification of a novel amino acid α-tyrosine 93 within the cholinergic ligand-binding sites of the acetylcholine receptor by photolabeling. Additional evidence for a three-loop model of the cholinergic ligand-binding site. J. Biol. Chem. 265, 10430–10437 (1990).

    CAS  PubMed  Google Scholar 

  48. Middleton, R. E. & Cohen, J. B. Mapping of the acetylcholine binding site of the nicotinic acetylcholine receptor: [3H]nicotine as an agonist photoaffinity label. Biochemistry 30, 6987–6997 (1991).

    Article  CAS  PubMed  Google Scholar 

  49. Kurosaki, T. et al. Functional properties of nicotinic acetylcholine receptor subunits expressed in various combinations. FEBS Lett. 214, 253–258 (1987).

    Article  CAS  PubMed  Google Scholar 

  50. Blount, P. & Merlie, J. P. Molecular basis of the two nonequivalent ligand binding sites of the muscle nicotinic acetylcholine receptor. Neuron 3, 349–357 (1989).

    Article  CAS  PubMed  Google Scholar 

  51. Sine, S. M. & Claudio, T. γ- and δ-subunits regulate the affinity and the cooperativity of ligand binding to the acetylcholine receptor. J. Biol. Chem. 266, 19369–19377 (1991).

    CAS  PubMed  Google Scholar 

  52. Sine, S. M. Molecular dissection of subunit interfaces in the acetylcholine receptor: identification of residues that determine curare selectivity. Proc. Natl Acad. Sci. USA 90, 9436–9440 (1993).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  53. Wang, D., Chiara, D. C., Xie, Y. & Cohen, J. B. Probing the structure of the nicotinic acetylcholine receptor with 4-benzoylbenzoylcholine, a novel photoaffinity competitive antagonist. J. Biol. Chem. 275, 28666–28674 (2000).

    Article  CAS  PubMed  Google Scholar 

  54. Czajkowski, C. & Karlin, A. Structure of the nicotinic receptor acetylcholine-binding site. Identification of acidic residues in the δ subunit within 0.9 nm of the α subunit binding site disulfide. J. Biol. Chem. 270, 3160–3164 (1995).

    Article  CAS  PubMed  Google Scholar 

  55. Pedersen, S. E. & Cohen, J. B. d-Tubocurarine binding sites are located at α–γ and α–δ subunit interfaces of the nicotinic acetylcholine receptor. Proc. Natl Acad. Sci. USA 87, 2785–2789 (1990).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  56. Czajkowski, C. & Karlin, A. Agonist binding site of Torpedo electric tissue nicotinic acetylcholine receptor. A negatively charged region of the δ subunit within 0.9 nm of the α subunit binding site disulfide. J. Biol. Chem. 266, 22603–22612 (1991).

    CAS  PubMed  Google Scholar 

  57. Machold, J. et al. Photolabeling reveals the proximity of the α-neurotoxin binding site to the M2 helix of the ion channel in the nicotinic acetylcholine receptor. Proc. Natl Acad. Sci. USA 92, 7282–7286 (1995).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  58. Zhong, W. et al. From ab initio quantum mechanics to molecular neurobiology: a cation–π binding site in the nicotinic receptor. Proc. Natl Acad. Sci. USA 95, 12088–12093 (1998).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  59. Schmitt, J. D., Sharples, C. G. & Caldwell, W. S. Molecular recognition in nicotinic acetylcholine receptors: the importance of π–cation interactions. J. Med. Chem. 42, 3066–3074 (1999).

    Article  CAS  PubMed  Google Scholar 

  60. Martin, M. D. & Karlin, A. Functional effects on the acetylcholine receptor of multiple mutations of γAsp174 and δAsp180. Biochemistry 36, 10742–10750 (1997).

    Article  CAS  PubMed  Google Scholar 

  61. Akk, G., Zhou, M. & Auerbach, A. A mutational analysis of the acetylcholine receptor channel transmitter binding site. Biophys. J. 76, 207–218 (1999).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  62. Stauffer, D. A. & Karlin, A. Electrostatic potential of the acetylcholine binding sites in the nicotinic receptor probed by reactions of binding-site cysteines with charged methanethiosulfonates. Biochemistry 33, 6840–6849 (1994).

    Article  CAS  PubMed  Google Scholar 

  63. Osaka, H., Sugiyama, N. & Taylor, P. Distinctions in agonist and antagonist specificity conferred by anionic residues of the nicotinic acetylcholine receptor. J. Biol. Chem. 273, 12758–12765 (1998).

    Article  CAS  PubMed  Google Scholar 

  64. Karlin, A. Chemical modification of the active site of the acetylcholine receptor. J. Gen. Physiol. 54, 245S–264S (1969).

    Article  CAS  Google Scholar 

  65. Sullivan, D. A. & Cohen, J. B. Mapping the agonist binding site of the nicotinic acetylcholine receptor. Orientation requirements for activation by covalent agonist. J. Biol. Chem. 275, 12651–12660 (2000).

    Article  CAS  PubMed  Google Scholar 

  66. Cohen, J. B., Sharp, S. D. & Liu, W. S. Structure of the agonist-binding site of the nicotinic acetylcholine receptor. [3H]Acetylcholine mustard identifies residues in the cation-binding subsite. J. Biol. Chem. 266, 23354–23364 (1991).

    CAS  PubMed  Google Scholar 

  67. Armstrong, N. & Gouaux, E. Mechanisms for activation and antagonism of an AMPA-sensitive glutamate receptor: crystal structures of the GluR2 ligand binding core. Neuron 28, 165–181 (2000).The structure of the ligand-binding portion of the extracellular domain of a glutamate receptor (not a Cys-loop receptor) was solved to high resolution. This paper shows that ligands induce a graded change in this structure depending on their effectiveness as an activator.

    Article  CAS  PubMed  Google Scholar 

  68. Damle, V. N. & Karlin, A. Effects of agonists and antagonists on the reactivity of the binding site disulfide in acetylcholine receptor from Torpedo californica. Biochemistry 19, 3924–3932 (1980).

    Article  CAS  PubMed  Google Scholar 

  69. Steinbach, J. H. & Chen, Q. Antagonist and partial agonist actions of d-tubocurarine at mammalian muscle acetylcholine receptors. J. Neurosci. 15, 230–240 (1995).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  70. Revah, F. et al. Mutations in the channel domain alter desensitization of a neuronal nicotinic receptor. Nature 353, 846–849 (1991).

    Article  CAS  PubMed  Google Scholar 

  71. Mishina, M. et al. Location of functional regions of acetylcholine receptor α-subunit by site directed mutagenesis. Nature 313, 364–369 (1985).

    Article  CAS  PubMed  Google Scholar 

  72. Galzi, J. L. et al. Functional significance of aromatic amino acids from three peptide loops of the α7 neuronal nicotinic receptor site investigated by site-directed mutagenesis. FEBS Lett. 294, 198–202 (1991).

    Article  CAS  PubMed  Google Scholar 

  73. Sine, S. M., Quiram, P., Papanikolaou, F., Kreienkamp, H. J. & Taylor, P. Conserved tyrosines in the α subunit of the nicotinic acetylcholine receptor stabilize quaternary ammonium groups of agonists and curariform antagonists. J. Biol. Chem. 269, 8808–8816 (1994).

    CAS  PubMed  Google Scholar 

  74. Tomaselli, G. F., McLaughlin, J. T., Jurman, M. E., Hawrot, E. & Yellen, G. Mutations affecting agonist sensitivity of the nicotinic acetylcholine receptor. Biophys. J. 60, 721–727 (1991).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  75. O'Leary, M. E., Filatov, G. N. & White, M. M. Characterization of d-tubocurarine binding site of Torpedo acetylcholine receptor. Am. J. Physiol. 266, C648–C653 (1994).

    Article  CAS  PubMed  Google Scholar 

  76. Xie, Y. & Cohen, J. B. Contributions of Torpedo nicotinic acetylcholine receptor γTrp-55 and δTrp-57 to agonist and competitive antagonist function. J. Biol. Chem. 276, 2417–2426 (2001).These tryptophan residues were the first non- α-subunit residues to be identified that contribute to the ACh-binding site. The properties of mutants in these residues provide insight into the asymmetry of the binding sites and the induction of conformational change by the binding of (+)-tubocurarine.

    Article  CAS  PubMed  Google Scholar 

  77. Sine, S. M., Kreienkamp, H. J., Bren, N., Maeda, R. & Taylor, P. Molecular dissection of subunit interfaces in the acetylcholine receptor: identification of determinants of α-conotoxin M1 selectivity. Neuron 15, 205–211 (1995).

    Article  CAS  PubMed  Google Scholar 

  78. Chiara, D. C., Xie, Y. & Cohen, J. B. Structure of the agonist-binding sites of the Torpedo nicotinic acetylcholine receptor: affinity-labeling and mutational analyses identify γTyr-111/δArg-113 as antagonist affinity determinants. Biochemistry 38, 6689–6698 (1999).

    Article  CAS  PubMed  Google Scholar 

  79. Sine, S. M. Identification of equivalent residues in the γ, δ, and ɛ subunits of the nicotinic receptor that contribute to α-bungarotoxin binding. J. Biol. Chem. 272, 23521–23527 (1997).

    Article  CAS  PubMed  Google Scholar 

  80. Damle, V. N. & Karlin, A. Affinity labeling of one of two α-neurotoxin binding sites in acetylcholine receptor from Torpedo californica. Biochemistry 17, 2039–2045 (1978).

    Article  CAS  PubMed  Google Scholar 

  81. Martinez, K. L., Corringer, P. J., Edelstein, S. J., Changeux, J. P. & Mérola, F. Structural differences in the two agonist binding sites of the Torpedo nicotinic acetylcholine receptor revealed by time-resolved fluorescence spectroscopy. Biochemistry 39, 6979–6990 (2000).

    Article  CAS  PubMed  Google Scholar 

  82. McArdle, J. J. et al. Waglerin-1 selectively blocks the epsilon form of the muscle nicotinic acetylcholine receptor. J. Pharmacol. Exp. Ther. 289, 543–550 (1999).

    CAS  PubMed  Google Scholar 

  83. Molles, B. E. et al. Identification of residues at the α and ɛ subunit interfaces mediating species selectivity of Waglerin-1 for nicotinic acetylcholine receptors. J. Biol. Chem. 27 November 2001 [epub ahead of print].

  84. Osaka, H., Malany, S., Molles, B. E., Sine, S. M. & Taylor, P. Pairwise electrostatic interactions between α-neurotoxins and γ, δ, and ɛ subunits of the nicotinic acetylcholine receptor. J. Biol. Chem. 275, 5478–5484 (2000).

    Article  CAS  PubMed  Google Scholar 

  85. Edelstein, S. & Changeux, J. P. Allosteric transitions of the acetylcholine receptor. Adv. Protein Chem. 51, 121–184 (1998).

    Article  CAS  PubMed  Google Scholar 

  86. Lee, C. Y. Chemistry and pharmacology of polypeptide toxins in snake venoms. Annu. Rev. Pharmacol. 12, 265–286 (1972).

    Article  CAS  PubMed  Google Scholar 

  87. Changeux, J. P., Kasai, M. & Lee, C. Y. Use of a snake venom toxin to characterize the cholinergic receptor protein. Proc. Natl Acad. Sci. USA 67, 1241–1247 (1970).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  88. Miledi, R., Molinoff, P. & Potter, L. T. Isolation of the cholinergic receptor protein of Torpedo electric tissue. Nature 229, 554–557 (1971).

    Article  CAS  PubMed  Google Scholar 

  89. Tsetlin, V. Snake venom α-neurotoxins and other 'three-finger' proteins. Eur. J. Biochem. 264, 281–286 (1999).

    Article  CAS  PubMed  Google Scholar 

  90. Haggerty, J. G. & Froehner, S. C. Restoration of 125I-α-bungarotoxin binding activity to the α subunit of Torpedo acetylcholine receptor isolated by gel electrophoresis in sodium dodecyl sulfate. J. Biol. Chem. 256, 8294–8297 (1981).

    CAS  PubMed  Google Scholar 

  91. Wilson, P. T., Lentz, T. L. & Hawrot, E. Determination of the primary amino acid sequence specifying the α-bungarotoxin binding site on the α subunit of the acetylcholine receptor from Torpedo californica. Proc. Natl Acad. Sci. USA 82, 8790–8794 (1985).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  92. Neumann, D., Barchan, D., Safran, A., Gershoni, J. M. & Fuchs, S. Mapping of the α-bungarotoxin binding site within the α subunit of the acetylcholine receptor. Proc. Natl Acad. Sci. USA 83, 3008–3011 (1986).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  93. Samson, A. O., Chill, J. H., Rodriguez, E., Scherf, T. & Anglister, J. NMR mapping and secondary structure determination of the major acetylcholine receptor α-subunit determinant interacting with α-bungarotoxin. Biochemistry 40, 5464–5473 (2001).

    Article  CAS  PubMed  Google Scholar 

  94. Harel, M. et al. The binding site of acetylcholine receptor as visualized in the X-ray structure of a complex between α-bungarotoxin and a mimotope peptide. Neuron 32, 173–174 (2001).A remarkable tale is told of the development of a short synthetic peptide with high affinity for α-bungarotoxin, the crystallization of the complex, and the superposition of the structure on the AChBP. By homology, this reveals the mode of binding of the snake α-neurotoxins to the ACh receptor.

    Article  Google Scholar 

  95. Kreienkamp, H. J., Sine, S. M., Maeda, R. K. & Taylor, P. Glycosylation sites selectively interfere with α-toxin binding to the nicotinic acetylcholine receptor. J. Biol. Chem. 269, 8108–8114 (1994).

    CAS  PubMed  Google Scholar 

  96. Antil, S., Servent, D. & Menez, A. Variability among the sites by which curaremimetic toxins bind to Torpedo acetylcholine receptor, as revealed by identification of the functional residues of α-cobratoxin. J. Biol. Chem. 274, 34851–34858 (1999).

    Article  CAS  PubMed  Google Scholar 

  97. Spura, A. et al. Biotinylation of substituted cysteines in the nicotinic acetylcholine receptor reveals distinct binding modes for α-bungarotoxin and erabutoxin a. J. Biol. Chem. 275, 22452–22460 (2000).

    Article  CAS  PubMed  Google Scholar 

  98. Spura, A. et al. Probing the agonist domain of the nicotinic acetylcholine receptor by cysteine scanning mutagenesis reveals residues in proximity to the α-bungarotoxin binding site. Biochemistry 38, 4912–4921 (1999).

    Article  CAS  PubMed  Google Scholar 

  99. Gorne-Tschelnokow, U., Strecker, A., Kaduk, C., Naumann, D. & Hucho, F. The transmembrane domains of the nicotinic acetylcholine receptor contain α-helical and β structures. EMBO J. 13, 338–341 (1994).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  100. Methot, N., Ritchie, B. D., Blanton, M. P. & Baenziger, J. E. Structure of the pore-forming transmembrane domain of a ligand-gated ion channel. J. Biol. Chem. 276, 23726–23732 (2001).

    Article  CAS  PubMed  Google Scholar 

  101. Akabas, M. H., Kaufmann, C., Archdeacon, P. & Karlin, A. Identification of acetylcholine receptor channel-lining residues in the entire M2 segment of the α subunit. Neuron 13, 919–927 (1994).

    Article  CAS  PubMed  Google Scholar 

  102. Zhang, H. & Karlin, A. Contribution of the β subunit M2 segment to the ion-conducting pathway of the acetylcholine receptor. Biochemistry 37, 7952–7964 (1998).The application of SCAM to 104 cysteine-substitution mutants of two membrane-spanning segments of two ACh receptor subunits is summarized. The modification of one of the mutants causes the appearance of multiple single-channel subconductance states and channel lifetimes.

    Article  CAS  PubMed  Google Scholar 

  103. Akabas, M. H. & Karlin, A. Identification of acetylcholine receptor channel-lining residues in the M1 segment of the α subunit. Biochemistry 34, 12496–12500 (1995).

    Article  CAS  PubMed  Google Scholar 

  104. Zhang, H. & Karlin, A. Identification of acetylcholine receptor channel-lining residues in the M1 segment of the β subunit. Biochemistry 36, 15856–15864 (1997).

    Article  CAS  PubMed  Google Scholar 

  105. Blanton, M. P. & Cohen, J. B. Identifying the lipid–protein interface of the Torpedo nicotinic acetylcholine receptor: secondary structure implication. Biochemistry 33, 2859–2872 (1994).

    Article  CAS  PubMed  Google Scholar 

  106. Blanton, M. P., Dangott, L. J., Raja, S. K., Lala, A. K. & Cohen, J. B. Probing the structure of the nicotinic acetylcholine receptor ion channel with the uncharged photoactivable compound [3H]-diazofluorene. J. Biol. Chem. 273, 8659–8668 (1998).

    Article  CAS  PubMed  Google Scholar 

  107. Claudio, T., Ballivet, M., Patrick, J. & Heinemann, S. Nucleotide and deduced amino acid sequences of Torpedo californica acetylcholine receptor γ subunit. Proc. Natl Acad. Sci. USA 80, 1111–1115 (1983).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  108. Devillers-Thiery, A., Giraudat, J., Bentaboulet, M. & Changeux, J.-P. Complete mRNA coding sequence of the acetylcholine binding α subunit of Torpedo marmorata acetylcholine receptor: a model for the transmembrane organization of the polypeptide chain. Proc. Natl Acad. Sci. USA 80, 2067–2071 (1983).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  109. Noda, M. et al. Structural homology of Torpedo californica acetylcholine receptor subunits. Nature 302, 528–532 (1983).

    Article  CAS  PubMed  Google Scholar 

  110. Tamamizu, S. et al. Functional effects of periodic tryptophan substitutions in the α M4 transmembrane domain of the Torpedo californica nicotinic acetylcholine receptor. Biochemistry 39, 4666–4673 (2000).

    Article  CAS  PubMed  Google Scholar 

  111. Hille, B. Ionic Channels of Excitable Membranes (Sinauer Associates, Sunderland, Massachusetts, 1992).

    Google Scholar 

  112. Sakmann, B. Nobel Lecture. Elementary steps in synaptic transmission revealed by currents through single ion channels. Neuron 8, 613–629 (1992).

    Article  CAS  PubMed  Google Scholar 

  113. Dani, J. A. Open channel structure and ion binding sites of the nicotinic acetylcholine receptor channel. J. Neurosci. 9, 884–892 (1989).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  114. Eisenberg, R. Computing the field in proteins and channels. J. Membr. Biol. 150, 1–25 (1996).

    Article  CAS  PubMed  Google Scholar 

  115. Green, M. E. & Lu, J. Monte-Carlo simulation of the effects of charges on water and ions in a tapered pore. J. Colloid Interface Sci. 171, 117–126 (1995).

    Article  CAS  Google Scholar 

  116. Morais-Cabral, J. H., Zhou, Y. & MacKinnon, R. Energetic optimization of ion conduction rate by the K+ selectivity filter. Nature 414, 37–42 (2001).

    Article  CAS  PubMed  Google Scholar 

  117. Zhou, Y., Morais-Cabral, J. H., Kaufman, A. & MacKinnon, R. Chemistry of ion coordination and hydration revealed by a K+ channel–Fab complex at 2.0 Å resolution. Nature 414, 43–48 (2001).In references 116 and 117 , the mechanism of ion conduction in a K+ channel is revealed in exquisite detail. These papers should be avoided by the envious.

    Article  CAS  PubMed  Google Scholar 

  118. Villarroel, A., Herlitze, S., Koenen, M. & Sakmann, B. Location of a threonine residue in the α-subunit M2 transmembrane segment that determines the ion flow through the acetylcholine receptor channel. Proc. R. Soc. Lond. B 243, 69–74 (1991).

    Article  CAS  Google Scholar 

  119. Konno, T. et al. Rings of anionic amino acids as structural determinants of ion selectivity in the acetylcholine receptor channel. Proc. R. Soc. Lond. B 244, 69–79 (1991).

    Article  CAS  Google Scholar 

  120. Imoto, K. et al. A ring of uncharged polar amino acids as a component of channel constriction in the nicotinic acetylcholine receptor. FEBS Lett. 289, 193–200 (1991).

    Article  CAS  PubMed  Google Scholar 

  121. Cohen, B. N., Labarca, C., Davidson, N. & Lester, H. A. Mutations in M2 alter the selectivity of the mouse nicotinic acetylcholine receptor for organic and alkali metal cations. J. Gen. Physiol. 100, 373–400 (1992).

    Article  CAS  PubMed  Google Scholar 

  122. Corringer, P. J. et al. Mutational analysis of the charge selectivity filter of the α7 nicotinic acetylcholine receptor. Neuron 22, 831–843 (1999).By painstaking alterations in the sequence of M2, the authors determine the necessary and sufficient conditions for switching from cation and to anion selectivity. The result is amazing and somewhat mysterious.

    Article  CAS  PubMed  Google Scholar 

  123. Wilson, G. G. & Karlin, A. The location of the gate in the acetylcholine receptor channel. Neuron 20, 1269–1281 (1998).A new approach to locating a gate is applied to the ACh receptor, and the result is controversial.

    Article  CAS  PubMed  Google Scholar 

  124. Wilson, G. G. & Karlin, A. Acetylcholine channel structure in the resting, open, and desensitized states probed with the substituted-cysteine-accessibility method. Proc. Natl Acad. Sci. USA 98, 1241–1248 (2001).Widespread differences in the structure of M2 in the different states of the receptor are rationalized in terms of gating and gates.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  125. Imoto, K. et al. Location of a δ-subunit region determining ion transport through the acetylcholine receptor channel. Nature 324, 670–674 (1986).

    Article  CAS  PubMed  Google Scholar 

  126. Imoto, K. et al. Rings of negatively charged amino acids determine the acetylcholine receptor channel conductance. Nature 335, 645–648 (1988).

    Article  CAS  PubMed  Google Scholar 

  127. Giraudat, J., Dennis, M., Heidmann, T., Chang, J.-Y. & Changeux, J.-P. Structure of the high-affinity binding site for noncompetitive blockers of the acetylcholine receptor: serine-262 of the δ subunit is labeled by [3H]chlorpromazine. Proc. Natl Acad. Sci. USA 83, 2719–2723 (1986).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  128. Giraudat, J. et al. Structure of the high-affinity binding site for noncompetitive blockers of the acetylcholine receptor: [3H]chlorpromazine labels homologous residues in the β and δ chains. Biochemistry 26, 2410–2418 (1987).

    Article  CAS  PubMed  Google Scholar 

  129. Hucho, F., Oberthur, W. & Lottspeich, F. The ion channel of the nicotinic acetylcholine receptor is formed by the homologous helices M II of the receptor subunits. FEBS Lett. 205, 137–142 (1986).

    Article  CAS  PubMed  Google Scholar 

  130. DiPaola, M., Kao, P. N. & Karlin, A. Mapping the α-subunit site photolabeled by the noncompetitive inhibitor [3H]quinacrine azide in the active state of the nicotinic acetylcholine receptor. J. Biol. Chem. 265, 11017–11029 (1990).

    CAS  PubMed  Google Scholar 

  131. Akabas, M. H., Stauffer, D. A., Xu, M. & Karlin, A. Acetylcholine receptor channel structure probed in cysteine-substitution mutants. Science 258, 307–310 (1992).

    Article  CAS  PubMed  Google Scholar 

  132. Pascual, J. M. & Karlin, A. State-dependent accessibility and electrostatic potential in the channel of the acetylcholine receptor: inferences from rates of reaction of thiosulfonates with substituted cysteines in the M2 segment of the α subunit. J. Gen. Physiol. 111, 717–739 (1998).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  133. Wilson, G. G., Pascual, J. M., Brooijmans, N., Murray, D. & Karlin, A. The intrinsic electrostatic potential and the intermediate ring of charge in the acetylcholine receptor channel. J. Gen. Physiol. 115, 93–106 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  134. Heidmann, T. & Changeux, J. P. Time-resolved photolabeling by the noncompetitive blocker chlorpromazine of the acetylcholine receptor in its transiently open and closed ion channel conformations. Proc. Natl Acad. Sci. USA 81, 1897–1901 (1984).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  135. Cox, R. N., Kaldany, R. R., DiPaola, M. & Karlin, A. Time-resolved photolabeling by quinacrine azide of a noncompetitive inhibitor site of the nicotinic acetylcholine receptor in a transient, agonist-induced state. J. Biol. Chem. 260, 7186–7193 (1985).

    CAS  PubMed  Google Scholar 

  136. White, B. H. & Cohen, J. B. Agonist-induced changes in the structure of the acetylcholine receptor M2 regions revealed by photoincorporation of an uncharged nicotinic noncompetitive antagonist. J. Biol. Chem. 267, 15770–15783 (1992).

    CAS  PubMed  Google Scholar 

  137. McCarthy, M. P. & Moore, M. A. Effects of lipids and detergents on the conformation of the nicotinic acetylcholine receptor from Torpedo californica. J. Biol. Chem. 267, 7655–7663 (1992).

    CAS  PubMed  Google Scholar 

  138. Bertrand, D., Galzi, J. L., Devillers-Thiery, A., Bertrand, S. & Changeux, J. P. Mutations at two distinct sites within the channel domain M2 alter calcium permeability of neuronal α7 nicotinic receptor. Proc. Natl Acad. Sci. USA 90, 6971–6975 (1993).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  139. Labarca, C. et al. Channel gating governed symmetrically by conserved leucine residues in the M2 domain of nicotinic receptors. Nature 376, 514–516 (1995).

    Article  CAS  PubMed  Google Scholar 

  140. Filatov, G. N. & White, M. M. The role of conserved leucines in the M2 domain of the acetylcholine receptor in channel gating. Mol. Pharmacol. 48, 379–384 (1995).

    CAS  PubMed  Google Scholar 

  141. Kosolapov, A. V., Filatov, G. N. & White, M. M. Acetylcholine receptor gating is influenced by the polarity of amino acids at position 9′ in the M2 domain. J. Membr. Biol. 174, 191–197 (2000).

    Article  CAS  PubMed  Google Scholar 

  142. Grosman, C. & Auerbach, A. Asymmetric and independent contribution of the second transmembrane segment 12′ residues to diliganded gating of acetylcholine receptor channels: a single-channel study with choline as the agonist. J. Gen. Physiol. 115, 637–651 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  143. Grosman, C., Salamone, F. N., Sine, S. M. & Auerbach, A. The extracellular linker of muscle acetylcholine receptor channels is a gating control element. J. Gen. Physiol. 116, 327–340 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  144. Wang, H. L. et al. Acetylcholine receptor M3 domain: stereochemical and volume contributions to channel gating. Nature Neurosci. 2, 226–233 (1999).

    Article  CAS  PubMed  Google Scholar 

  145. Bouzat, C., Barrantes, F. & Sine, S. Nicotinic receptor fourth transmembrane domain: hydrogen bonding by conserved threonine contributes to channel gating kinetics. J. Gen. Physiol. 115, 663–672 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  146. DaCosta, C. J., Ogrel, A. A., McCardy, E. A., Blanton, M. P. & Baenziger, J. E. Lipid–protein interactions at the nicotinic acetylcholine receptor: a functional coupling between nicotinic receptors and phosphatidic acid-containing lipid bilayers. J. Biol. Chem. 277, 201–208 (2002).The profound effects of the lipid environment on receptor structure and function are reviewed and further shown.

    Article  CAS  PubMed  Google Scholar 

  147. Wang, H. L. et al. Fundamental gating mechanism of nicotinic receptor channel revealed by mutation causing a congenital myasthenic syndrome. J. Gen. Physiol. 116, 449–462 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  148. Unwin, N. Acetylcholine receptor channel imaged in the open state. Nature 373, 37–43 (1995).

    Article  CAS  PubMed  Google Scholar 

  149. Takahama, K. & Klee, M. R. Voltage clamp analysis of the kinetics of piperidine-induced chloride current in isolated Aplysia neurons. Naunyn Schmiedebergs Arch. Pharmacol. 342, 575–581 (1990).

    Article  CAS  PubMed  Google Scholar 

  150. Kehoe, J. & McIntosh, J. M. Two distinct nicotinic receptors, one pharmacologically similar to the vertebrate α7-containing receptor, mediate Cl currents in Aplysia neurons. J. Neurosci. 18, 8198–8213 (1998).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  151. Adams, D. J., Dwyer, T. M. & Hille, B. The permeability of endplate channels to monovalent and divalent metal cations. J. Gen. Physiol. 75, 493–510 (1980).

    Article  CAS  PubMed  Google Scholar 

  152. Lewis, C. A. & Stevens, C. F. Acetylcholine receptor channel ionic selectivity: ions experience an aqueous environment. Proc. Natl Acad. Sci. USA 80, 6110–6113 (1983).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  153. Fieber, L. A. & Adams, D. J. Acetylcholine-evoked currents in cultured neurones dissociated from rat parasympathetic cardiac ganglia. J. Physiol. (Lond.) 434, 215–237 (1991).

    Article  CAS  Google Scholar 

  154. Vernino, S., Amador, M., Luetje, C. W., Patrick, J. & Dani, J. A. Calcium modulation and high calcium permeability of neuronal nicotinic acetylcholine receptors. Neuron 8, 127–134 (1992).

    Article  CAS  PubMed  Google Scholar 

  155. Katz, E. et al. High calcium permeability and calcium block of the α9 nicotinic acetylcholine receptor. Hear. Res. 141, 117–128 (2000).

    Article  CAS  PubMed  Google Scholar 

  156. Cohen, B. N., Labarca, C., Czyzyk, L., Davidson, N. & Lester, H. A. Tris+/Na+ permeability ratios of nicotinic acetylcholine receptors are reduced by mutations near the intracellular end of the M2 region. J. Gen. Physiol. 99, 545–572 (1992).

    Article  CAS  PubMed  Google Scholar 

  157. Villarroel, A., Herlitze, S., Witzemann, V., Koenen, M. & Sakmann, B. Asymmetry of the rat acetylcholine receptor subunits in the narrow region of the pore. Proc. R. Soc. Lond. B 249, 317–324 (1992).

    Article  CAS  Google Scholar 

  158. Gunthorpe, M. J. & Lummis, S. C. Conversion of the ion selectivity of the 5-HT3A receptor from cationic to anionic reveals a conserved feature of the ligand-gated ion channel superfamily. J. Biol. Chem. 276, 10977–10983 (2001). | PubMed |

    Article  CAS  PubMed  Google Scholar 

  159. Keramidas, A., Moorhouse, A. J., French, C. R., Schofield, P. R. & Barry, P. H. M2 pore mutations convert the glycine receptor channel from being anion- to cation-selective. Biophys. J. 79, 247–259 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  160. Adcock, C., Smith, G. R. & Sansom, M. S. The nicotinic acetylcholine receptor: from molecular model to single-channel conductance. Eur. Biophys. J. 29, 29–37 (2000).

    Article  CAS  PubMed  Google Scholar 

  161. Yakel, J. L., Lagrutta, A., Adelman, J. P. & North, R. A. Single amino acid substitution affects desensitization of the 5-hydroxytryptamine type 3 receptor expressed in Xenopus oocytes. Proc. Natl Acad. Sci. USA 90, 5030–5033 (1993).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  162. Xu, M. & Akabas, M. H. Identification of channel-lining residues in the M2 membrane-spanning segment of the GABAA receptor α1 subunit. J. Gen. Physiol. 107, 195–205 (1996).

    Article  CAS  PubMed  Google Scholar 

  163. Karlin, A. & Akabas, M. H. Substituted-cysteine accessibility method. Methods Enzymol. 293, 123–145 (1998).

    Article  CAS  PubMed  Google Scholar 

  164. Javitch, J. A., Li, X., Kaback, J. & Karlin, A. A cysteine residue in the third membrane-spanning segment of the human D2 dopamine receptor is exposed in the binding-site crevice. Proc. Natl Acad. Sci. USA 91, 10355–10359 (1994).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  165. Javitch, J. A., Fu, D., Chen, J. & Karlin, A. Mapping the binding-site crevice of the dopamine D2 receptor by the substituted-cysteine accessibility method. Neuron 14, 825–831 (1995).

    Article  CAS  PubMed  Google Scholar 

  166. Bruice, T. W. & Kenyon, G. L. Novel alkyl alkanethiosulfonate sulfhydryl reagents. Modification of derivatives of l-cysteine. J. Protein Chem. 1, 47–58 (1982).

    Article  CAS  Google Scholar 

  167. Roberts, D. D., Lewis, S. D., Ballou, D. P., Olson, S. T. & Shafer, J. A. Reactivity of small thiolate anions and cysteine-25 in papain toward methyl methanethiosulfonate. Biochemistry 25, 5595–5601 (1986).

    Article  CAS  PubMed  Google Scholar 

  168. Kaback, H. R. A molecular mechanism for energy coupling in a membrane transport protein, the lactose permease of Escherichia coli. Proc. Natl Acad. Sci. USA 94, 5539–5543 (1997).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Center for Molecular Recognition, and Departments of Biochemistry and Molecular Biophysics, Physiology and Cellular Biophysics, and Neurology, Columbia University, New York, 10032, New York, USA

    Arthur Karlin

Authors
  1. Arthur Karlin
    View author publications

    You can also search for this author in PubMed Google Scholar

Related links

Related links

DATABASES

Entrez Protein

AChBP

α-bungarotoxin

conotoxin MI

erabutoxin 

LocusLink

α1-subunit

α2–α10

β1-subunit

β2–β4

δ-subunit

ɛ-subunit

γ-subunit

GABAA receptor

GluR2

glycine receptors

5-HT3 receptor 

Protein Data Bank

1FTO: GluR2 S1S2, apo state

1HC9: α-bungarotoxin, complex with high-affinity peptide

1I9B: acetylcholine-binding protein (AChBP)

FURTHER INFORMATION

ion channels

nicotinic acetylcholine receptors

nicotinic acetylcholine receptors in muscle

nicotinic acetylcholine receptors in neurons 

Families of Transport Proteins

Ligand-Gated Ion Channel Database

The Ion Channel Web Page

Glossary

CURARE

A poisonous extract from certain tropical vines, which blocks neuromuscular transmission, causing relaxation and paralysis. The active component in curare is (+)-tubocurarine.

HYDROPATHY PLOT

A plot that allows the visualization of hydrophobicity patterns in a peptide sequence, and is particularly useful in determining the membrane-spanning regions of proteins. Obtaining a plot requires the use of a hydropathy scale that is based on the hydrophobic and hydrophilic properties of the 20 amino acids. A moving window determines the summed hydropathy at each point in the sequence, and this value is then plotted against the amino-acid positions.

ELECTROCYTE

A generic name for the cells of the electric organ of electric fish.

ALLOSTERIC

A term used to describe proteins that have two or more binding sites, in which the occupancy of each site affects the affinities of the others.

MONOD–WYMAN–CHANGEUX MODEL

A model that is used to describe the nature of allosteric interactions in oligomeric proteins. It requires the protomers to be associated such that all of them have equivalent positions. The protomers must exist in two forms — tense (ligand-free) and relaxed (ligand-bound) — that are in equilibrium. Ligand binding causes a concerted change in the protomers, and the binding curve for an allosteric protein can then be calculated from the so-called allosteric constant, which depends on the ratio between the tense and the relaxed forms and their dissociation constants.

310 HELIX

A structural feature that consists of three amino-acid residues per turn, and a 2-Å helix translation per residue.

CRYO-ELECTRON MICROSCOPY

A microscopy method in which the specimen of interest is suspended in buffer, sprayed on a copper mesh, and dipped into an extremely cold liquid such as liquid ethane. The extremely cold temperature turns the buffer into a layer of ice, trapping the specimen inside it. The advantage of this method is that the specimen is largely preserved in its native state.

AFFINITY LABELLING

A method for labelling the functional parts of a protein, such as a receptor, by covalently linking a tagged agonist, antagonist or other molecule that the protein normally binds.

COREY–PAULING–KOLTUN REPRESENTATION

A space-filling atomic model in which the atoms are represented as spheres, the radii of which are proportional to the van der Waals radius of the atom.

CATION–π INTERACTION

A non-covalent interaction between a cation and the face of an aromatic ring.

QUATERNARY AMMONIUM ION

An ammonium ion in which the nitrogen is bonded to four carbons.

EC50

The concentration of agonist that evokes a half-maximal response.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Karlin, A. Emerging structure of the Nicotinic Acetylcholine receptors. Nat Rev Neurosci 3, 102–114 (2002). https://doi.org/10.1038/nrn731

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1038/nrn731

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing