A Cation-pi Interaction in the Binding Site of the Glycine Receptor Is Mediated by a Phenylalanine Residue

作者：Pless Stephan A; Millen Kat S; Hanek Ariele P; Lynch Joseph W; Lester Henry A; Lummis Sarah C R^*; Dougherty Dennis A

来源：Journal of Neuroscience, 2008, 28(43): 10937-10942.

DOI：10.1523/JNEUROSCI.2540-08.2008

• ligand-gated ion channel
• Cys-loop receptor
• cation-pi interaction
• unnatural amino acids
• nonsense suppression
• neurotransmitter

Cys-loop receptor binding sites characteristically contain many aromatic amino acids. In nicotinic ACh and 5-HT3 receptors, a Trp residue forms a cation-pi interaction with the agonist, whereas in GABA(A) receptors, a Tyr performs this role. The glycine receptor binding site, however, contains predominantly Phe residues. Homology models suggest that two of these Phe side chains, Phe159 and Phe207, and possibly a third, Phe63, are positioned such that they could contribute to a cation-pi interaction with the primary amine of glycine. Here, we test this hypothesis by incorporation of a series of fluorinated Phe derivatives using unnatural amino acid mutagenesis. The data reveal a clear correlation between the glycine EC50 value and the cation-pi binding ability of the fluorinated Phe derivatives at position 159, but not at positions 207 or 63, indicating a single cation-pi interaction between glycine and Phe159. The data thus provide an anchor point for locating glycine in its binding site, and demonstrate for the first time a cation-pi interaction between Phe and a neurotransmitter.

• 出版日期2008-10-22