Identification of a New Component of the Agonist Binding Site of the Nicotinic 7 Homooligomeric Receptor

Pierre-Jean Corringer (1) , Jean-Luc Galzi (1) , Jean-Luc Eiselé (1) , Sonia Bertrand (2) , Jean-Pierre Changeux (1, 3) , Daniel Bertrand (2)

1 Neurobiologie moléculaire
2 CMU - Centre médical universitaire de Genève
3 RC - Récepteurs et Cognition

Tryptophan 54 of the alpha 7 neuronal nicotinic homooligomeric receptor is homologous to gamma-Trp-55 and delta-Trp-57 of non-alpha subunits of Torpedo receptor labeled by d-tubocurarine. This residue was mutated on the alpha 7-V201-5-hydroxytryptamine (5HT)3 homooligomeric chimera, which displays alpha 7 nicotinic pharmacology, and for which both equilibrium binding studies and electrophysiological recordings could be carried out in parallel. Replacement of Trp-54 by a Phe, Ala, or His causes a progressive decrease both in binding affinity and in responses (EC50 or IC50) for acetylcholine, nicotine, and dihydro-beta-erythroidine, without significant modification in alpha-Bgtx binding. Except for Gln-56, comparatively small effects are observed when the other residues of the 52-58 region are mutated into alanine. These data support the participation of Trp-54 to ligand binding, and provide evidence for a new "complementary component" of the alpha 7 nicotinic binding site, distinct from its three-loop "principal component," and homologous to the "non-alpha component" present on gamma and delta subunits.

Domaines: Chimie

Pierre-Jean Corringer, Jean-Luc Galzi, Jean-Luc Eiselé, Sonia Bertrand, Jean-Pierre Changeux, et al.. Identification of a New Component of the Agonist Binding Site of the Nicotinic 7 Homooligomeric Receptor. Journal of Biological Chemistry, 1995, 270 (20), pp.11749 - 11752. ⟨10.1074/jbc.270.20.11749⟩. ⟨pasteur-01714720⟩