Structural and functional diversity in vertebrate skeletal muscle nicotinic acetylcholine receptors.

Overall, the data support the conclusion that the gamma and epsilon subunits explain major features of the functional diversity of vertebrate muscle nAChR. They cannot account, however, for all observed functional diversity. It is not clear whether additional subunits exist or whether some posttranslational modifications produce the functional differences. Work is underway to correlate structural features of the muscle nicotinic AChR with functional properties. To date, the results demonstrate that each known subunit can affect receptor kinetic parameters and/or channel conductance. Two remaining sets of questions must be answered. The first lies within the field of cell biology: What subunits are expressed, do posttranslational modifications underlie functional modifications, and what structural changes are associated with physiologically relevant changes in function? The second is more strictly of structure-function relationships: What are the functional parameters of structurally defined nAChRs and can structural features be correlated with function?