Two Amino Acid Residues Contribute to a Cation-π Binding Interaction in the Binding Site of an Insect GABA Receptor
Abstract
Cys-loop receptor binding sites characteristically possess an "aromatic box," where several aromatic amino acid residues surround the bound ligand. A cation-π interaction between one of these residues and the natural agonist is common, although the residue type and location are not conserved. Even in the closely related vertebrate GABA_A and GABA_C receptors, residues in distinct locations perform this role: in GABA_A receptors, a Tyr residue in loop A forms a cation-π interaction with GABA, while in GABA_C receptors it is a loop B residue. GABA-activated Cys-loop receptors also exist in invertebrates, where they have distinct pharmacologies and are the target of a range of pesticides. Here we examine the location of GABA in an insect binding site by incorporating a series of fluorinated Phe derivatives into the receptor binding pocket using unnatural amino acid mutagenesis, and evaluating the resulting receptors when expressed in Xenopus oocytes. A homology model suggests that two aromatic residues (in loops B and C) are positioned such that they could contribute to a cation-π interaction with the primary ammonium of GABA, and the data reveal a clear correlation between the GABA EC_(50) and the cation-π binding ability both at Phe206 (loop B) and Tyr254 (loop C), demonstrating for the first time the contribution of two aromatic residues to a cation-π interaction in a Cys-loop receptor.
Additional Information
© 2011 the authors. Received March 31, 2011; revised June 8, 2011; accepted June 24, 2011. We thank The Wellcome Trust (WT 81925; S.C.R.L. is a Wellcome Trust Senior Research Fellow in Basic Biomedical Science), the Medical Research Council (a studentship to I.M.), the European Union (FP7 NeuroCypres; J.A.A., S.C.R.L.), and the U.S. National Institutes of Health (NS34407, D.A.D.). Author contributions: S.C.R.L. designed research; S.C.R.L., I.M., and J.A.A. performed research; D.A.D. contributed unpublished reagents/analytic tools; S.C.R.L., I.M., and J.A.A. analyzed data; S.C.R.L. and D.A.D. wrote the paper.Attached Files
Published - Lummis2011p15719J_Neurosci.pdf
Files
Name | Size | Download all |
---|---|---|
md5:2618115fa7607cdb78de9f62dafb9321
|
1.0 MB | Preview Download |
Additional details
- PMCID
- PMC3233689
- Eprint ID
- 25286
- Resolver ID
- CaltechAUTHORS:20110912-080631961
- Wellcome Trust
- WT 81925
- Medical Research Council (UK)
- European Union
- NIH
- NS34407
- Created
-
2011-09-12Created from EPrint's datestamp field
- Updated
-
2021-11-09Created from EPrint's last_modified field