Determination of alpha-conotoxin binding modes on neuronal nicotinic acetylcholine receptors.
alpha-Conotoxins, from cone snails, and alpha-neurotoxins, from snakes, are competitive inhibitors of nicotinic acetylcholine receptors (nAChRs) that have overlapping binding sites in the ACh binding pocket. These disulphide-rich peptides are used extensively as tools to localize and pharmacologically characterize specific nAChRs subtypes. Recently, a homology model based on the high-resolution structure of an ACh binding protein (AChBP) allowed the three-fingered alpha-neurotoxins to be docked onto the alpha7 nAChR. To investigate if alpha-conotoxins interact with the nAChR in a similar manner, we built homology models of human alpha7 and alpha3beta2 nAChRs, and performed docking simulations of alpha-conotoxins ImI, PnIB, PnIA and MII using the program GOLD. Docking revealed that alpha-conotoxins have a different mode of interaction compared with alpha-neurotoxins, with surprisingly few nAChR residues in common between their overlapping binding sites. These docking experiments show that ImI and PnIB bind to the ACh binding pocket via a small cavity located above the beta9/beta10 hairpin of the (+)alpha7 nAChR subunit. Interestingly, PnIB, PnIA and MII were found to bind in a similar location on alpha7 or alpha3beta2 receptors mostly through hydrophobic interactions, while ImI bound further from the ACh binding pocket, mostly through electrostatic interactions. These findings, which distinguish alpha-conotoxin and alpha-neurotoxin binding modes, have implications for the rational design of selective nAChR antagonists.
Dutertre
Sébastien
S
Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
Nicke
Annette
A
Tyndall
Joel D A
JD
Lewis
Richard J
RJ
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003198:Computer Simulation; D020916:Conotoxins / Q000737:chemistry / Q000378:metabolism*; D006531:HEPES / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D020916:Conotoxins; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D006531:HEPES