title: Characterization of a glycine receptor domain that controls the binding and gating mechanisms of the beta-amino acid agonist, taurine.
abstract: The beta-amino acid, taurine, is a full agonist of the human glycine receptor alpha1 subunit when recombinantly expressed in a mammalian (HEK293) cell line, but a partial agonist of the same receptor when expressed in Xenopus oocytes. Several residues in the Ala101-Thr112 domain have previously been identified as determinants of beta-amino acid binding and gating mechanisms in Xenopus oocyte-expressed receptors. The present study used the substituted cysteine accessibility method to investigate the role of this domain in controlling taurine-specific binding and gating mechanisms of glycine receptors recombinantly expressed in mammalian cells. Asn102 and Glu103 are identified as taurine and glycine binding sites, whereas Ala101 is eliminated as a possible binding site. The N102C mutation also abolished the antagonistic actions of taurine, indicating that this site does not discriminate between the putative agonist- and antagonist-bound conformations of beta-amino acids. The effects of mutations from Lys104-Thr112 indicate that the mechanism by which this domain controls beta-amino acid-specific binding and gating processes differs substantially depending on whether the receptor is expressed in mammalian cells or Xenopus oocytes. Thr112 is the only domain element in mammalian cell-expressed GlyRs which was demonstrated to discriminate between glycine and taurine.
authors.affiliation: Department of Physiology and Pharmacology, School of Biomedical Sciences, University of Queensland, Brisbane, Australia.
authors.forename: N L
authors.initials: NL
authors.lastname: Han
authors.forename: J L
authors.initials: JL
authors.lastname: Haddrill
authors.forename: J W
authors.initials: JW
authors.lastname: Lynch
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites / Q000502:physiology; D002460:Cell Line; D003545:Cysteine / Q000235:genetics; D005998:Glycine / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007668:Kidney / Q000166:cytology; D008698:Mesylates / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D017434:Protein Structure, Tertiary; D018009:Receptors, Glycine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013654:Taurine / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D008698:Mesylates; D018009:Receptors, Glycine; D013439:Sulfhydryl Reagents; C109153:(2-sulfonatoethyl)methanethiosulfonate; C109154:(2-(trimethylammonium)ethyl)methanethiosulfonate; D013654:Taurine; D003545:Cysteine; D005998:Glycine