TY - JOUR T1 - Efficient Binding of 4/7 α-conotoxins to Nicotinic α4β2 Receptors is Prevented by R185 and P195 in the α4 Subunit JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.112.078683 SP - mol.112.078683 AU - Mirko Beissner AU - Sebastien Dutertre AU - Rudolf Schemm AU - Timm Danker AU - Annett Sporning AU - Helmut Grubmuller AU - Annette Nicke Y1 - 2012/01/01 UR - http://molpharm.aspetjournals.org/content/early/2012/07/16/mol.112.078683.abstract N2 - &α-Conotoxins are subtype-selective nAChR antagonists. While potent [alpha]3β2 nAChR-selective α-contoxins have been identified, currently characterized α-conotoxins show no or only weak affinity for α4β2 nAChRs, which are besides α7 receptors the most abundant nAChRs in the mammalian brain. To identify the determinants responsible for this difference, we substituted selected amino acid residues in the ligand binding domain of the α4 subunit by the corresponding residues in the α3 subunit. Two-electrode voltage-clamp analysis of these mutants revealed increased affinity of α-conotoxins MII, TxIA, and [A10L]TxIA at the α4(R185I)β2 receptor. Conversely, α-conotoxin potency was reduced at the reverse α3(I186R)β2 mutant. Replacement of α4R185 by alanine, glutamate, and lysine demonstrated that a positive charge in this position prevents α-conotoxin binding. Combination of the R185I mutation with a P195Q mutation outside the binding site but in loop C completely transferred high α-conotoxin potency to the α4β2 receptor. Molecular dynamics simulations of homology models with docked α-conotoxin indicate that these residues control access to the α-conotoxin binding site. ER -