Kouvatsos_2016_Proc.Natl.Acad.Sci.U.S.A_113_9635

In this study we report the X-ray crystal structure of the extracellular domain (ECD) of the human neuronal alpha2 nicotinic acetylcholine receptor (nAChR) subunit in complex with the agonist epibatidine at 3.2 A. Interestingly, alpha2 was crystallized as a pentamer, revealing the intersubunit interactions in a wild type neuronal nAChR ECD and the full ligand binding pocket conferred by two adjacent alpha subunits. The pentameric assembly presents the conserved structural scaffold observed in homologous proteins, as well as distinctive features, providing unique structural information of the binding site between principal and complementary faces. Structure-guided mutagenesis and electrophysiological data confirmed the presence of the alpha2(+)/alpha2(-) binding site on the heteromeric low sensitivity alpha2beta2 nAChR and validated the functional importance of specific residues in alpha2 and beta2 nAChR subunits. Given the pathological importance of the alpha2 nAChR subunit and the high sequence identity with alpha4 (78%) and other neuronal nAChR subunits, our findings offer valuable information for modeling several nAChRs and ultimately for structure-based design of subtype specific drugs against the nAChR associated diseases.