Structural correlates of human muscle nicotinic acetylcholine receptor subunit assembly mediated by δ(+) interface residues

Abstract Muscle nicotinic acetylcholine receptors are a class of heteropentameric ligand-gated cation channels with constituent subunits adopting a fixed stoichiometric arrangement. The specific amino acid residues that govern subunit ordering are however, only partially understood. By integrating all-atom molecular dynamics simulations, bioinformatics, two-electrode voltage clamp electrophysiology and 125 I-α-bungarotoxin assays of chimeric nAChR subunits, we identify residues across the extracellular, transmembrane and extended M4 helix of the δ subunit that make structural signatures that contribute to intransigent assembly rules. Furthermore, functional differences observed in α 2 δ 2 β receptors can be rationalized by changes in dynamical behavior that manifest themselves at the agonist binding site.