An amino acid substitution in the pore region of a glutamate-gated chloride channel enables the coupling of ligand binding to channel gating.
Many of the subunits of ligand-gated ion channels respond poorly, if at all, when expressed as homomeric channels in Xenopus oocytes. This lack of a ligand response has been thought to result from poor surface expression, poor assembly, or lack of an agonist binding domain. The Caenorhabditis elegans glutamate-gated chloride channel subunit GluClbeta responds to glutamate as a homomeric channel while the GluClalpha subunit is insensitive. A chimera between GluClalpha and GluClbeta was used to suggest that major determinants for glutamate binding are present on the GluClalpha N terminus. Amino acid substitutions in the presumed pore of GluClalpha conferred direct glutamate gating indicating that GluClalpha is deficient in coupling of ligand binding to channel gating. Heteromeric channels of GluClalpha+beta may differ from the prototypic muscle nicotinic acetylcholine receptor in that they have the potential to bind ligand to all of the subunits forming the channel.
Etter
A
A
Merck Research Laboratories, Department of Cell Biochemistry, Rahway, New Jersey 07065-0900, USA.
Cully
D F
DF
Schaeffer
J M
JM
Liu
K K
KK
Arena
J P
JP
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans; D002462:Cell Membrane / Q000502:physiology; D018118:Chloride Channels / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D003001:Cloning, Molecular / Q000379:methods; D004331:Drosophila melanogaster; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating; D007559:Ivermectin / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D017354:Point Mutation; D017433:Protein Structure, Secondary; D011978:Receptors, Nicotinic / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D018118:Chloride Channels; D046911:Macromolecular Substances; D011978:Receptors, Nicotinic; D011993:Recombinant Fusion Proteins; D018698:Glutamic Acid; D004533:Egtazic Acid; D007559:Ivermectin; C052102:22,23-dihydroavermectin B(1)a; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid