THE EXTRACELLULAR DISULFIDE LOOP MOTIF OF THE INHIBITORY GLYCINE RECEPTOR DOES NOT FORM THE AGONIST BINDING-SITE

Abstract

Inhibitory (glycine and gamma-aminobutyric acid type A) and excitatory (nicotinic acetylcholine and serotonin 5-hydroxytryptamine type 3) receptors of the ligand-gated ion channel superfamily are related by both structural similarities and primary sequence identity. One invariant feature of all members of this receptor superfamily is the presence of an extracellular disulfide loop motif. This structural motif has been modeled, and Cockcroft et al. [Proteins 8:386-397 (1990)] have suggested that it forms the agonist binding site of the ligand-gated ion channel receptors. Using site-directed mutagenesis of the inhibitory glycine receptor (GlyR), we have specifically tested this hypothesis. The..