Waglerin-1 (Wtx-1) is a 22-amino acid peptide that competitively antagonizes muscle nicotinic @entity934 receptors (nAChRs). Previous work demonstrated that Wtx-1 binds to @entity19 nAChRs with higher affinity than receptors from @entity35 or @entity1 , and distinguished residues in alpha and epsilon subunits that govern the species selectivity. These studies also showed that Wtx-1 binds selectively to the alpha-epsilon binding site with significantly higher affinity than to the alpha-delta binding site. Here we identify residues at equivalent positions in the epsilon, gamma, and delta subunits that govern Wtx-1 selectivity for one of the two binding sites on the @entity6786 pentamer. Using a series of chimeric and point mutant subunits, we show that residues @entity4022 -57, @entity2574 -59, Tyr-111, Tyr-115, and @entity2574 -173 of the epsilon subunit account predominantly for the 3700-fold higher affinity of the alpha-epsilon site relative to that of the alpha-gamma site. Similarly, we find that residues Lys-34, @entity4022 -57, @entity2574 -59, and @entity2574 -173 account predominantly for the high affinity of the alpha-epsilon site relative to that of the alpha-delta site. Analysis of combinations of point mutations reveals that @entity2574 -173 in the epsilon subunit is required together with the remaining determinants in the epsilon subunit to achieve Wtx-1 selectivity. In particular, Lys-34 interacts with @entity2574 -173 to confer high affinity, resulting in a DeltaDeltaG(INT) of -2.3 kcal/mol in the epsilon subunit and a DeltaDeltaG(INT) of -1.3 kcal/mol in the delta subunit. @entity2574 -173 is part of a nonhomologous insertion not found in the @entity934 binding protein structure. The key role of this insertion in Wtx-1 selectivity indicates that it is proximal to the ligand binding site. We use the binding and interaction energies for Wtx-1 to generate structural models of the alpha-epsilon, alpha-gamma, and alpha-delta binding sites containing the nonhomologous insertion.

Residues in the epsilon subunit of the nicotinic XXXX receptor interact to confer selectivity of waglerin-1 for the alpha-epsilon subunit interface site.

@entity1 :: ('9606', 'Species') :: ['humans'] @entity19 :: ('10090', 'Species') :: ['mouse'] @entity4022 :: ('MESH:C066286', 'Chemical') :: ['Gly'] @entity6786 :: ('1137', 'Gene') :: ['nAChR'] @entity35 :: ('10116', 'Species') :: ['rats'] @entity2574 :: ('CHEBI:22660', 'Chemical') :: ['Asp'] @entity934 :: ('MESH:D000109', 'Chemical') :: ['acetylcholine']
@entity934 :: (MESH:D000109,Chemical) :: ['acetylcholine']
