To study pathways by which acetylcholine receptor (AChR) subunits might assemble, Torpedo alpha subunits were expressed in Xenopus oocytes alone or in combination with beta, gamma, or delta subunits. The maturation of the conformation of the main immunogenic region (MIR) on alpha subunits was measured by binding of mAbs and the maturation of the conformation of the AChR binding site on alpha subunits was measured by binding of alpha-bungarotoxin (alpha Bgt) and cholinergic ligands. The size of subunits and subunit complexes was assayed by sedimentation on sucrose gradients. It is generally accepted that native AChRs have the subunit composition alpha 2 beta gamma delta. Torpedo alpha subunits expressed alone resulted in an amorphous range of complexes with little affinity for alpha Bgt or mAbs to the MIR, rather than in a unique 5S monomeric assembly intermediate species. A previously recognized temperature-dependent failure in alpha subunit maturation may cause instability of the monomeric assembly intermediate and accumulation of aggregated denatured alpha subunits. Coexpression of alpha with beta subunits also resulted in an amorphous range of complexes. However, coexpression of alpha subunits with gamma or delta subunits resulted in the efficient formation of 6.5S alpha gamma or alpha delta complexes with high affinity for mAbs to the MIR, alpha Bgt, and small cholinergic ligands. These alpha gamma and alpha delta subunit pairs may represent normal assembly intermediates in which Torpedo alpha is stabilized and matured in conformation. Coexpression of alpha, gamma, and delta efficiently formed 8.8S complexes, whereas complexes containing alpha beta and gamma or alpha beta and delta subunits are formed less efficiently. Assembly of beta subunits with complexes containing alpha gamma and delta subunits may normally be a rate-limiting step in assembly of AChRs.
Skip Nav Destination
Article navigation
1 March 1991
Article|
March 01 1991
Assembly of Torpedo acetylcholine receptors in Xenopus oocytes.
M S Saedi,
M S Saedi
Salk Institute for Biological Studies, La Jolla, California 92093.
Search for other works by this author on:
W G Conroy,
W G Conroy
Salk Institute for Biological Studies, La Jolla, California 92093.
Search for other works by this author on:
J Lindstrom
J Lindstrom
Salk Institute for Biological Studies, La Jolla, California 92093.
Search for other works by this author on:
M S Saedi
Salk Institute for Biological Studies, La Jolla, California 92093.
W G Conroy
Salk Institute for Biological Studies, La Jolla, California 92093.
J Lindstrom
Salk Institute for Biological Studies, La Jolla, California 92093.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1991) 112 (5): 1007–1015.
Citation
M S Saedi, W G Conroy, J Lindstrom; Assembly of Torpedo acetylcholine receptors in Xenopus oocytes.. J Cell Biol 1 March 1991; 112 (5): 1007–1015. doi: https://doi.org/10.1083/jcb.112.5.1007
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionEmail alerts
Advertisement
Advertisement