Abstract
Three families of ligand-activated ion channels mediate synaptic communication between excitable cells in mammals. For pentameric channels related to nicotinic acetylcholine receptors and tetrameric channels such as glutamate receptors, the pore-forming and gate regions have been studied extensively. In contrast, little is known about the structure of trimeric P2X receptor channels, a family of channels that are activated by ATP and are important in neuronal signaling, pain transmission and inflammation. To identify the pore-forming and gate regions in P2X receptor channels, we introduced cysteine residues throughout the two transmembrane (TM) segments and studied their accessibility to thiol-reactive compounds and ions. Our results show that TM2 lines the central ion-conduction pore, TM1 is positioned peripheral to TM2 and the flow of ions is minimized in the closed state by a gate formed by the external region of TM2.
Publication types
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Research Support, N.I.H., Intramural
MeSH terms
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Amino Acid Substitution / genetics
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Animals
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Cadmium Compounds / pharmacology
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Cell Line
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Cell Membrane / metabolism
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Cysteine / genetics
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Cysteine / metabolism
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Humans
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Ion Channel Gating / drug effects
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Ion Channel Gating / genetics*
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Ion Channel Gating / physiology*
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Kidney / cytology
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Kidney / drug effects
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Kidney / metabolism
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Mesylates / pharmacology
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Models, Biological
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Mutagenesis, Site-Directed
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Patch-Clamp Techniques
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Protein Structure, Tertiary / genetics
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Protein Structure, Tertiary / physiology
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Rats
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Receptors, Purinergic P2 / drug effects
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Receptors, Purinergic P2 / genetics*
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Receptors, Purinergic P2 / metabolism*
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Receptors, Purinergic P2X2
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Silver Nitrate / pharmacology
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Transfection
Substances
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Cadmium Compounds
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Mesylates
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P2RX2 protein, human
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Receptors, Purinergic P2
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Receptors, Purinergic P2X2
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(2-(trimethylammonium)ethyl)methanethiosulfonate
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Silver Nitrate
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Cysteine