Determination of the α-Conotoxin Vc1.1 Binding Site on the α9α10 Nicotinic Acetylcholine Receptor

a-Conotoxin Vc1.1 specifically and potently inhibits the nicotinic acetylcholine receptor subtype alpha 9 alpha 10 (alpha 9 alpha 10 nAChR) and is a potential novel treatment for neuropathic pain. Here, we used a combination of computational modeling and electrophysiology experiments to determine the Vc1.1 binding site on the alpha 9 alpha 10 nAChR. Interactions of Vc1.1 with two probable binding sites, alpha 9 alpha 10 and alpha 10 alpha 9, were modeled. Mutational energies calculated by assuming specific interactions in the alpha 10 alpha 9 binding site correlated better with electrophysiological recordings than those assuming interactions with the alpha 9 alpha 10 binding site. Two novel Vc1.1 analogues, [N9F]Vc1.1 and [N9W]Vc1.1, were predicted to have large differences in affinity between the two binding sites. Data from functional studies were consistent with computational predictions that assumed preferred binding of Vc1.1 to the alpha 10 alpha 9 pocket. Moreover, our modeling study suggested that a single hydrogen bond formed between Vc1.1 and position 59 of the alpha 10 alpha 9 pocket confers specificity to rat versus human alpha 9 alpha 10 nAChRs.