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Control of P2X2 Channel Permeability by the Cytosolic Domain

Eickhorst, Angela N. and Berson, Amy and Cockayne, Debra and Lester, Henry A. and Khahk, Baljit S. (2002) Control of P2X2 Channel Permeability by the Cytosolic Domain. Journal of General Physiology, 120 (2). pp. 119-131. ISSN 0022-1295. http://resolver.caltech.edu/CaltechAUTHORS:EICjgp02

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Abstract

ATP-gated P2X channels are the simplest of the three families of transmitter-gated ion channels. Some P2X channels display a time- and activation-dependent change in permeability as they undergo the transition from the relatively Na+-selective I1 state to the I2 state, which is also permeable to organic cations. We report that the previously reported permeability change of rat P2X2 (rP2X2) channels does not occur at mouse P2X2 (mP2X2) channels expressed in oocytes. Domain swaps, species chimeras, and point mutations were employed to determine that two specific amino acid residues in the cytosolic tail domain govern this difference in behavior between the two orthologous channels. The change in pore diameter was characterized using reversal potential measurements and excluded field theory for several organic ions; both rP2X2 and mP2X2 channels have a pore diameter of ~11 Å in the I1 state, but the transition to the I2 state increases the rP2X2 diameter by at least 3 Å. The I1 to I2 transition occurs with a rate constant of ~0.5 s^-1. The data focus attention on specific residues of P2X2 channel cytoplasmic domains as determinants of permeation in a state-specific manner.


Item Type:Article
Additional Information:© 2002 Rockefeller University Press Submitted: 20 November 2001. Revised: 13 May 2002 Accepted: 15 May 2002. Published online 15 July 2002 doi:10.1085/jgp.20028535 We thank K. Kostenko and H. Li for help with preparation of Xenopus oocytes, G. Shapovalov for measurements of 2-(methyl-amino)-ethanol mobility, other members of the group for comments, and Nigel Unwin for discussion and comments on the paper. Work in our labs was supported by a Wellcome Trust (UK) Prize Fellowship, Roche Bioscience, National Institutes of Health (NS-11756), and the Medical Research Council.
Subject Keywords:ATP; ion channel; modulation; P2X; purinoceptor
Record Number:CaltechAUTHORS:EICjgp02
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:EICjgp02
Alternative URL:http://dx.doi.org/10.1085/jgp.20028535
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6242
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:29 Nov 2006
Last Modified:26 Dec 2012 09:19

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