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Direct gating of ATP-activated ion channels (P2X2 receptors) by lipophilic attachment at the outer end of the second transmembrane domain
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Rothwell, Simon W., Stansfeld, Phillip J., Bragg, Laricia, Verkhratsky, Alexej and North, R. Alan (2013) Direct gating of ATP-activated ion channels (P2X2 receptors) by lipophilic attachment at the outer end of the second transmembrane domain. Journal of Biological Chemistry, 289 (2). pp. 618-626. doi:10.1074/jbc.M113.529099 ISSN 0021-9258.
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Official URL: http://dx.doi.org/10.1074/jbc.M113.529099
Abstract
The ionic pore of the P2X receptor passes through the central axis of six transmembrane (TM) helices, two from each of three subunits. Val48 and Ile328 are at the outer end of TM1 and TM2, respectively. Homology models of the open and closed states of P2X2 indicate that pore opening is associated with a large lateral displacement of Ile328. In addition, molecular dynamics simulations suggest that lipids enter the interstices between the outer ends of the TM domains. The P2X2(I328C) receptor was activated by propyl-methanethiosulfonate (MTS) as effectively as by ATP, but cysteine substitutions elsewhere in TM2 had no such effect. Other lipophilic MTS compounds (methyl, ethyl, and tert-butylethyl) had a similar effect but not polar MTS. The properties of the conducting pathway opened by covalent attachment of propyl-MTS were the same as those opened by ATP, with respect to unitary conductance, rectification, and permeability of N-methyl-D-glucamine. The ATP-binding residue Lys69 was not required for the action of propyl-MTS, although propyl-MTS did not open P2X2(K308A/I328C) receptors. The propyl-MTS did not open P2X2 receptors in which the Val48 side chain was removed (P2X2(V48G/I328C)). The results suggest that an interaction between Val48 and Ile328 stabilizes the closed channel and that this is broken by covalent attachment of a larger lipophilic moiety at the I328C receptors. Lipid intercalation between the separating TM domains during channel opening would be facilitated in P2X2(I328C) receptors with attached propyl-MTS. The results are consistent with the channel opening mechanism proposed on the basis of closed and open crystal structures and permit the refinement of the position of the TMs within the bilayer.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) | ||||
Journal or Publication Title: | Journal of Biological Chemistry | ||||
Publisher: | American Society for Biochemistry and Molecular Biology | ||||
ISSN: | 0021-9258 | ||||
Official Date: | 10 January 2013 | ||||
Dates: |
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Volume: | 289 | ||||
Number: | 2 | ||||
Page Range: | pp. 618-626 | ||||
DOI: | 10.1074/jbc.M113.529099 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Open Access (Creative Commons) |
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