Members of the Cys-loop family of transmitter-gated ion channels are pentameric membrane proteins that respond to the binding of transmitter with a conformational change resulting in the opening of a gate and an increased affinity to the agonist. The muscle-type nicotinic acetylcholine receptor (nAChR) has served as a prototype in Cys-loop ion channel research due to its large single-channel conductance resulting in a high signal-to-noise ratio, and the relatively simple kinetic properties. In the nAChR, the two transmitter binding sites are located in the extracellular domain of the receptor at the interfaces between an a and a d subunit, and an a and an e. The subunit in the fifth position (b) is not directly involved in transmitter binding. The focus of this proposal is the non-transmitter-binding b subunit. We will use a combination of molecular biological, electrophysiological, and kinetic analyses approaches to determine the energetics and timing of gating motions in: i) the second membrane-spanning domain, ii) the extracellular region, and iii) the region comprising the linker between the second and third membrane-spanning regions and the pre-TM1 region. The work will elucidate the involvement of the b subunit in the conformational changes that lead to channel activation, and provide insight into the sources of molecular motions in the non- transmitter-binding subunit. The completion of the proposed work will increase our understanding of how transmitter-gated ion channels function, and how the non-transmitter-binding subunit shapes receptor function.
The nicotinic acetylcholine receptor mediates fast synaptic transmission in the vertebrate neuromuscular junction. The pentameric protein contains two transmitter binding sites located at subunit-subunit interfaces. This project is aimed at elucidating the role of the fifth subunit, which is not involved in transmitter binding, in the structural motions resulting in channel gating.
Li, Ping; Eaton, Megan M; Steinbach, Joe Henry et al. (2013) The benzodiazepine diazepam potentiates responses of ?1?2?2L ?-aminobutyric acid type A receptors activated by either ?-aminobutyric acid or allosteric agonists. Anesthesiology 118:1417-25 |
Akk, Gustav; Eaton, Megan; Li, Ping et al. (2013) Energetic contributions to channel gating of residues in the muscle nicotinic receptor ?1 subunit. PLoS One 8:e78539 |