title: An acetylcholine receptor precursor alpha subunit that binds alpha-bungarotoxin but not d-tubocurare.
abstract: We have identified an intracellular form of the alpha subunit of the acetylcholine receptor that binds alpha-bungarotoxin with high affinity. Unlike the mature receptor complex, an alpha 2 beta gamma delta pentamer that migrates as a 9S species in velocity sedimentation analysis, the intracellular species moves as a 5S component. The kinetics of appearance of alpha subunit in the 5S component and the mature receptor complex indicate that the intracellular 5S component is a precursor of the mature receptor. The precursor species differs from 9S receptor in two critical features: (i) the precursor alpha subunit is not associated with beta subunit and (ii) alpha-bungarotoxin binding to the precursor alpha subunit is not inhibited by the cholinergic ligands decamethonium or d-tubocurarine. The properties of the precursor suggest that the acquisition of the ligand binding site by alpha subunit occurs at a distinct stage in the posttranslational development of functional acetylcholine receptor.
authors.forename: B E
authors.initials: BE
authors.lastname: Carlin
authors.forename: J C
authors.initials: JC
authors.lastname: Lawrence
authors.forename: J M
authors.initials: JM
authors.lastname: Lindstrom
authors.forename: J P
authors.initials: JP
authors.lastname: Merlie
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001667:Binding, Competitive; D002038:Bungarotoxins / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation; D008970:Molecular Weight; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D011978:Receptors, Nicotinic / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014403:Tubocurarine / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D002038:Bungarotoxins; D011498:Protein Precursors; D011978:Receptors, Nicotinic; D004247:DNA; D014403:Tubocurarine