Photolabeling the Torpedo Nicotinic Acetylcholine Receptor with 4-Azido-2,3,5,6-tetrafluorobenzoylcholine, a Partial Agonist

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Title Photolabeling the Torpedo Nicotinic Acetylcholine Receptor with 4-Azido-2,3,5,6-tetrafluorobenzoylcholine, a Partial Agonist
Author Nirthanan, S. Niru; Ziebell, Michael R.; Chiara, David C.; Hong, Filbert; Cohen, Jonathan B.
Journal Name Biochemistry
Year Published 2005
Place of publication Washington, DC
Publisher American Chemical Society
Abstract The interactions of a photoreactive analogue of benzoylcholine, 4-azido-2,3,5,6-tetrafluorobenzoylcholine (APFBzcholine), with nicotinic acetylcholine receptors (nAChRs) were studied using electrophysiology and photolabeling. APFBzcholine acted as a low-efficacy partial agonist, eliciting maximal responses that were 0.3 and 0.1% of that of acetylcholine for embryonic mouse and Torpedo nAChRs expressed in Xenopus oocytes, respectively. Equilibrium binding studies of [3H]APFBzcholine with nAChR-rich membranes from Torpedo electric organ revealed equal affinities (Keq = 12 μM) for the two agonist binding sites. Upon UV irradiation at 254 nm, [3H]APFBzcholine was photoincorporated into the nAChR α, γ, and δ subunits in an agonist-inhibitable manner. Photolabeled amino acids in the agonist binding sites were identified by Edman degradation of isolated, labeled subunit fragments. [3H]APFBzcholine photolabeled γLeu-109/δLeu-111, γTyr-111, and γTyr-117 in binding site segment E as well as αTyr-198 in α subunit binding site segment C. The observed pattern of photolabeling is examined in relation to the predicted orientation of the azide when APFBzcholine is docked in the agonist binding site of a homology model of the nAChR extracellular domain based upon the structure of the snail acetylcholine binding protein.
Peer Reviewed Yes
Published Yes
Alternative URI http://dx.doi.org/10.1021/bi051209y
Volume 44
Issue Number 41
Page from 13447
Page to 13456
ISSN 0006-2960
Date Accessioned 2009-07-09
Language en_AU
Research Centre Griffith Health Institute
Faculty Griffith Health Faculty
Subject Basic Pharmacology; Receptors and Membrane Biology
URI http://hdl.handle.net/10072/25851
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1x

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