title: Subunit arrangement in P2X receptors.
abstract: ATP-gated ionotropic receptors (P2X receptors) are distributed widely in the nervous system. For example, a hetero-oligomeric receptor containing both P2X2 and P2X3 subunits is involved in primary afferent sensation. Each subunit has two membrane-spanning domains. We have used disulfide bond formation between engineered cysteines to demonstrate close proximity between the outer ends of the first transmembrane domain of one subunit and the second transmembrane domain of another. After expression in HEK 293 cells of such modified P2X2 or P2X4 subunits, the disulfide bond formation is evident because an ATP-evoked channel opening requires previous reduction with dithiothreitol. In the hetero-oligomeric P2X2/3 receptor the coexpression of doubly substituted subunits with wild-type partners allows us to deduce that the hetero-oligomeric channel contains adjacent P2X3 subunits but does not contain adjacent P2X2 subunits. The results suggest a "head-to-tail" subunit arrangement in the quaternary structure of P2X receptors and show that a trimeric P2X2/3 receptor would have the composition P2X2(P2X3)2.
authors.affiliation: Institute of Molecular Physiology, University of Sheffield, Sheffield S10 2TN, United Kingdom.
authors.forename: Lin-Hua
authors.initials: LH
authors.lastname: Jiang
authors.forename: Miran
authors.initials: M
authors.lastname: Kim
authors.forename: Valeria
authors.initials: V
authors.lastname: Spelta
authors.forename: Xuenong
authors.initials: X
authors.lastname: Bo
authors.forename: Annmarie
authors.initials: A
authors.lastname: Surprenant
authors.forename: R Alan
authors.initials: RA
authors.lastname: North
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008024:Ligands; D046911:Macromolecular Substances; D018408:Patch-Clamp Techniques; D015202:Protein Engineering; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D014162:Transfection
chemical_list: D004220:Disulfides; D008024:Ligands; D046911:Macromolecular Substances; C546401:P2RX2 protein, human; C546407:P2RX3 protein, human; D021122:Protein Subunits; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate