title: alpha-Conotoxin EI, a new nicotinic acetylcholine receptor antagonist with novel selectivity.
abstract: We report the isolation and characterization of a novel nicotinic acetylcholine receptor (nAChR) ligand. The toxin is an 18 amino acid peptide and is the first reported alpha-conotoxin from an Atlantic fish-hunting Conus. The peptide was purified from the venom of Conus ermineus and is called alpha-conotoxin EI. The sequence diverges from that of previously isolated alpha-conotoxins. We demonstrate that this structural divergence has functional consequences. In Torpedo nAChRs, alpha-conotoxin EI selectively binds the agonist site near the alpha/delta subunit interface in contrast to alpha-conotoxin MI which selectively targets the alpha/gamma agonist binding site. In mammalian nAChRs alpha-conotoxin EI shows high affinity for both the alpha/delta and alpha/gamma subunit interfaces (with some preference for the alpha/delta site), whereas alpha-conotoxin MI is highly selective for the alpha/delta ligand binding site. The sequence of the peptide is: Arg-Asp-Hyp-Cys-Cys-Tyr-His-Pro-Thr-Cys-Asn-Met-Ser-Asn-Pro-Gln-Ile-Cys- NH2, with disulfide bridging between Cys4-Cys10 and Cys5-Cys18, analogous to those of previously described alpha-conotoxins. This sequence has been verified by total chemical synthesis. Thus, alpha-conotoxin EI is a newly-available tool with unique structure and function for characterization of nAChRs.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City 84112, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Martinez
authors.forename: B M
authors.initials: BM
authors.lastname: Olivera
authors.forename: W R
authors.initials: WR
authors.lastname: Gray
authors.forename: A G
authors.initials: AG
authors.lastname: Craig
authors.forename: D R
authors.initials: DR
authors.lastname: Groebe
authors.forename: S N
authors.initials: SN
authors.lastname: Abramson
authors.forename: J M
authors.initials: JM
authors.lastname: McIntosh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020916:Conotoxins; D005399:Fishes; D008969:Molecular Sequence Data; D018733:Nicotinic Antagonists / Q000302:isolation & purification* / Q000378:metabolism; D010455:Peptides / Q000302:isolation & purification* / Q000378:metabolism; D011869:Radioligand Assay; D011978:Receptors, Nicotinic / Q000378:metabolism; D014118:Toxins, Biological / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D020916:Conotoxins; D018733:Nicotinic Antagonists; D010455:Peptides; D011978:Receptors, Nicotinic; D014118:Toxins, Biological; C096701:conotoxin EI