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  • The EMBO Journal (2003) 22, 1990 - 2003
  • doi:10.1093/emboj/cdg197



There is an Erratum (June 2003) associated with this Article.

An H-bond between two residues from different loops of the acetylcholine binding site contributes to the activation mechanism of nicotinic receptors

Thomas Grutter1, Lia Prado de Carvalho2, Nicolas Le Novère1, Pierre Jean Corringer1, Stuart Edelstein1,3 and Jean-Pierre Changeux1

  1. Institut Pasteur, URA 2182 CNRS 'Récepteurs et Cognition', Département des Biotechnologies, 25 rue du Dr Roux, 75724 Paris cedex 15, France
  2. Université Pierre et Marie Curie, UMR 7102 CNRS 'Neurobiologie des Processus Adaptatifs', 7 quai St Bernard, 75005 Paris, France
  3. Département de Biochimie, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland

Correspondence to:

Thomas Grutter, E-mail: grutter@pasteur.fr

Jean-Pierre Changeux, E-mail: changeux@pasteur.fr

Received 10 December 2002; Accepted 5 March 2003; Revised 17 February 2003

The molecular mechanisms of nicotinic receptor activation are still largely unknown. The crystallographic structure of the acetylcholine binding protein (AChBP) reveals a single H-bond between two different acetylcholine binding loops. Within these homologous loops we systematically introduced alpha4 residues into the alpha7/5HT3 chimeric receptor and found that the single point mutations G152K (loop B) and P193I (loop C) displayed a non-additive increase of equilibrium binding affinity for several agonists compared with the double mutant G152K/P193I. In whole-cell patch–clamp recordings, G152K, P193I and G152K/P193I mutants displayed an increase up to 5-fold in acetylcholine potency with a large decrease of the apparent Hill coefficients (significantly smaller than one). Concomitantly, the G152K/P193I mutant showed a dramatic loss of high-affinity alpha-bungarotoxin binding (100-fold decrease), thus pinpointing a new contact area for the toxin. Fitting the data with an allosteric–kinetic model, together with molecular dynamic simulations, suggests that the presence of the inter-backbone H-bond between positions 152 and 193, revealed in alpha4 and in alpha7 double mutant but not in alpha7, coincides with a large stabilization of both open and desensitized states of nicotinic receptors.

  • Keywords:

    • activation mechanism,
    • alpha-bungarotoxin binding,
    • H-bond,
    • myasthenic mutant,
    • neuronal nicotinic receptor