title: Mapping of the alpha-bungarotoxin binding site within the alpha subunit of the acetylcholine receptor.
abstract: Synthetic peptides and their respective antibodies have been used in order to map the alpha-bungarotoxin binding site within the alpha subunit of the acetylcholine receptor. By using antibodies to a synthetic peptide corresponding to residues 169-181 of the alpha subunit, we demonstrate that this sequence is included within the 18-kDa toxin binding fragment previously reported. Furthermore, the 18-kDa fragment was also found to bind a monoclonal antibody (5.5) directed against the cholinergic binding site. Sequential proteolysis of the acetylcholine receptor with trypsin, prior to Staphylococcus aureus V8 protease digestion, resulted in a 15-kDa toxin binding fragment that is included within the 18-kDa fragment but is shorter than it only at its carboxyl terminus. This 15-kDa fragment therefore initiates beyond Asp-152 and terminates in the region of Arg-313/Lys-314. In addition, experiments are reported that indicate that in the intact acetylcholine receptor, Cys-128 and/or Cys-142 are not crosslinked by disulfide bridges with any of the cysteines (at positions 192, 193, and 222) that reside in the 15-kDa toxin binding fragment. Finally, the synthetic dodecapeptide Lys-His-Trp-Val-Tyr-Tyr-Thr-Cys-Cys-Pro-Asp-Thr, which is present in the 15-kDa fragment (corresponding to residues 185-196 of the alpha subunit) was shown to bind alpha-bungarotoxin directly. This binding was completely inhibited by competition with d-tubocurarine.
authors.forename: D
authors.initials: D
authors.lastname: Neumann
authors.forename: D
authors.initials: D
authors.lastname: Barchan
authors.forename: A
authors.initials: A
authors.lastname: Safran
authors.forename: J M
authors.initials: JM
authors.lastname: Gershoni
authors.forename: S
authors.initials: S
authors.lastname: Fuchs
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004220:Disulfides; D010446:Peptide Fragments / Q000032:analysis; D011817:Rabbits; D011950:Receptors, Cholinergic / Q000032:analysis*; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: D004220:Disulfides; D010446:Peptide Fragments; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor