AMPA receptors and bacterial periplasmic amino acid-binding proteins share the ionic mechanism of ligand recognition.
In order to identify key structural determinants for ligand recognition, we subjected the ligand-binding domain of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-selective glutamate receptor GluR-D subunit to site-directed mutagenesis. Based on the analysis of the [3H]AMPA-binding properties of the mutated binding sites, we constructed a revised three-dimensional model of the ligand-binding site, different in many respects from previously published models. In particular, our results indicate that the residues Arg507 and Glu727 represent the structural and functional correlates of Arg77 and Asp161 in the homologous bacterial lysine/ornithine/arginine-binding protein and histidine-binding protein, and directly interact with the alpha-carboxyl and alpha-amino group of the bound ligand, respectively. In contrast, Glu424, implicated previously in ionic interactions with the alpha-amino group of the agonist, is unlikely to have such a role in ligand binding. Our results indicate that glutamate receptors share with the bacterial polar amino acid-binding proteins the fundamental mechanism of amino acid recognition.
Department of Biosciences (Division of Biochemistry) and Institute of Biotechnology, P.O.Box 56, FIN-00014 University of Helsinki, Helsinki, Finland.
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Lampinen
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Pentikäinen
M S
MS
Johnson
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Keinänen
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002412:Cations; D002460:Cell Line; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D007313:Insecta; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011810:Quinoxalines / Q000494:pharmacology; D018091:Receptors, AMPA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017470:Receptors, Glutamate / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D002412:Cations; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D011994:Recombinant Proteins; D018698:Glutamic Acid; C056723:FG 9041