RT Journal Article
SR Electronic
T1 Efficient Binding of 4/7 α-Conotoxins to Nicotinic α4β2 Receptors Is Prevented by Arg185 and Pro195 in the α4 Subunit
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 711
OP 718
DO 10.1124/mol.112.078683
VO 82
IS 4
A1 Mirko Beissner
A1 Sébastien Dutertre
A1 Rudolf Schemm
A1 Timm Danker
A1 Annett Sporning
A1 Helmut Grubmüller
A1 Annette Nicke
YR 2012
UL http://molpharm.aspetjournals.org/content/82/4/711.abstract
AB α-Conotoxins are subtype-selective nicotinic acetylcholine receptor (nAChR) antagonists. Although potent α3β2 nAChR-selective α-conotoxins 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 α4Arg185 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.