title: Three possible disulfides in the acetylcholine receptor alpha-subunit.
abstract: The cysteinyl residues of the acetylcholine receptor alpha-subunit of Torpedo californica were analyzed. All seven cysteines could be accounted for. Three possible disulfide bridges and one unpaired cysteine were indicated. The disulfide linkages were as follows: Cys128 to Cys142; Cys192 to Cys193; Cys412 to Cys418 (Cys222 is unpaired). The identification of cysteinyl residues was accomplished by a modified protein blot procedure. Cysteinyl residues of intact nicotinic acetylcholine receptor were selectively biotinylated with 3-(N-maleimidopropionyl)biocytin and subsequently detected by the 125I-labeled avidin overlay of blotted Staphylococcus aureus V8 proteolyzed alpha-subunits. Two pairs of cysteines (Cys128/Cys142 and Cys412/Cys418) could be demonstrated only after Na(BH4) reduction of the acetylcholine receptor. Cysteine residues 192 and 193 are particularly sensitive to reduction; 0.1 mM dithiothreitol is sufficient.
mesh_terms: D000818:Animals; D001894:Borohydrides / Q000494:pharmacology; D002038:Bungarotoxins / Q000378:metabolism; D003545:Cysteine / Q000032:analysis; D004220:Disulfides / Q000032:analysis*; D005033:Ethylmaleimide / Q000494:pharmacology; D008239:Lysine / Q000031:analogs & derivatives / Q000494:pharmacology; D046911:Macromolecular Substances; D008301:Maleimides / Q000494:pharmacology; D010449:Peptide Mapping; D011950:Receptors, Cholinergic / Q000032:analysis*; D012697:Serine Endopeptidases / Q000378:metabolism; D014101:Torpedo
chemical_list: D001894:Borohydrides; D002038:Bungarotoxins; D004220:Disulfides; D046911:Macromolecular Substances; D008301:Maleimides; D011950:Receptors, Cholinergic; C025364:sodium borohydride; C047272:3-(N-maleimidopropionyl)biocytin; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase; D008239:Lysine; D003545:Cysteine; D005033:Ethylmaleimide