RT Journal Article
SR Electronic
T1 Structural Basis for Epibatidine Selectivity at Desensitized Nicotinic Receptors
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 123
OP 131
DO 10.1124/mol.104.003665
VO 67
IS 1
A1 Pennington, Richard A.
A1 Gao, Fan
A1 Sine, Steven M.
A1 Prince, Richard J.
YR 2005
UL http://molpharm.aspetjournals.org/content/67/1/123.abstract
AB The agonist binding sites of the fetal muscle nicotinic acetylcholine receptor are formed at the interfaces of α-subunits and neighboring γ- and δ-subunits. When the receptor is in the nonconducting desensitized state, the α-γ site binds the agonist epibatidine 200-fold more tightly than does the α-δ site. To determine the structural basis for this selectivity, we constructed γ/δ-subunit chimeras, coexpressed them with complementary wild-type subunits in HEK 293 cells, and determined epibatidine affinity of the resulting complexes. The results reveal three determinants of epibatidine selectivity: γ104–117/δ106–δ119, γ164–171/δ166–177, and γPro190/δAla196. Point mutations reveal that three sequence differences within the γ104–117/δ106–δ119 region are determinants of epibatidine selectivity: γLys104/δTyr106, γSer111/δTyr113, and γTyr117/δTyr119. In the δ-subunit, simultaneous mutation of these residues to their γ equivalent produces high affinity, γ-like epibatidine binding. However, converting γ to δ affinity requires replacement of the γ104–117 segment with δ sequence, suggesting interplay of residues in this region. The structural basis for epibatidine selectivity is explained by computational docking of epibatidine to a homology model of the α-γ binding site.