title: An aspartic acid residue near the second transmembrane segment of ATP receptor/channel regulates agonist sensitivity.
abstract: Charged or polarized amino acid residues near or within the second transmembrane (M2) segment of neuronal ATP receptor/channels (P2X2 receptors) were neutralized by site-directed mutagenesis, and the properties of the mutants were electrophysiologically characterized using Xenopus oocytes. When Asp315 was substituted with Val (D315V), the sensitivity to ATP was reduced by about 60-fold. The sensitivity to ATP was not affected by the neutralization of Lys324, which is involved in a Walker type A ATP-binding sequence, Lys366, Tyr330, or Asn333. With D315V channels, the sensitivities to other agonists (ADP, ATP gamma S, and 2-methylthio ATP) were also reduced. The sensitivities to antagonists (suramin and Cibacron Blue F3GA) were, however, not affected by this neutralization. The results suggest that Asp315, which is assumed to be present in the extracellular region near the M2 segment of P2X2 receptor/channels, serves to maintain agonist sensitivity.
authors.affiliation: Division of Pharmacology, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakazawa
authors.forename: Y
authors.initials: Y
authors.lastname: Ohno
authors.forename: K
authors.initials: K
authors.lastname: Inoue
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D001665:Binding Sites / Q000235:genetics; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D017354:Point Mutation; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000235:genetics; D058476:Receptors, Purinergic P2X2; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D000227:Adenine Nucleotides; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D011994:Recombinant Proteins; D001224:Aspartic Acid