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Title: Cysteine substitution mutants give structural insight and identify ATP binding and activation sites at P2X receptors
Authors: Roberts, Jonathan A.
Evans, Richard J.
First Published: 11-Apr-2007
Publisher: Society for Neuroscience
Citation: Journal of Neuroscience, 2007, 27(15), pp.4072-4082
Abstract: P2X receptors for extracellular ATP are a distinct family of ligand-gated cation channels involved in physiological processes ranging from synaptic transmission to muscle contraction. Common ATP binding motifs are absent from P2X receptors, and the extent of the agonist binding site is unclear. We used cysteine-scanning mutagenesis, radiolabeled 2-azido ATP binding, and methanethiosulfonate (MTS) compounds to identify amino acid residues involved in ATP binding and gating of the human P2X1 receptor. The pattern of MTSEA [(2-aminoethyl)methanethiosulfonate hydrobromide] biotinylation was also used to determine the accessibility of substituted cysteine residues and whether this changed on addition of ATP. Analysis of cysteine-substituted mutants of the last 44 amino acid residues (S286 –I329) in the extracellular loop before the second transmembrane segment showed that N290, F291, R292, and K309 mutants had reduced ATP potency and 2-azido ATP binding. MTS reagents produced additional shifts in ATP potency at these residues, suggesting that they are directly involved in ATP binding; the effects were dependent on the charge of the MTS reagent at K309C; one explanation for this is that K309 interacts directly with the negatively charged phosphate of ATP. The remainder of the cysteine substitutions had little or no effect on ATP potency. However, at the mutants D316C, G321C, A323C, and I328C, MTS reagents did not change ATP potency but modified agonist-evoked responses, suggesting that this region may contribute to the gating of the channel.
DOI Link: 10.1523/JNEUROSCI.2310-06.2007
ISSN: 0270-6474
eISSN: 1529-2401
Version: Publisher version
Status: Peer reviewed
Type: Article
Rights: Copyright © 2007 Society for Neuroscience. Deposited with reference to the publisher's archiving policy available on the SHERPA/RoMEO website. 6 months after publication, the work becomes available to the public to copy, distribute, or display under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license.
Description: Also available from the publisher website at, doi: 10.1523/JNEUROSCI.2310-06.2007. The author manuscript is available in UK PubMed Central, PMCID PMC2092412
Appears in Collections:Published Articles, Dept. of Cell Physiology and Pharmacology

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