Cell
Volume 34, Issue 3, October 1983, Pages 747-757
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Article
Assembly in vivo of mouse muscle acetylcholine receptor: Identification of an α subunit species that may be an assembly intermediate

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Abstract

We have studied assembly of acetylcholine receptor in vivo using subunit-specific monoclonal antibodies and immunoprecipitation with α-bungarotoxin and antitoxin. We have identified three distinct forms of the α subunit. The newly synthesized α subunit species has a sedimentation coefficient of 5S and is recognized only by antibody specific for SDS-denatured α subunit. We have called this species αs1. The 5S αTx species is not associated with β subunits and is probably monomeric. αTx is formed from αs1 with a half-time of 15 min and an efficiency of ⋍30%. Formation of αTx involves a conformational change, and we suggest that this conformation is dependent upon or stabilized by disulfide bond formation. The assembly of αTx with β subunits (and probably γ and δ) into a 9S complex appears to be an efficient but slow process requiring more than 90 min. Unassembled α61 subunits are degraded rapidly. However, subunit degradation is a result of failure to assemble, rather than its cause.

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