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Updated: Aug 8, 2026

Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
Published on: May 18, 2009
Ion permeation and block of P2X(2) purinoceptors: single channel recordings
1Department of Chemical Engineering, State University of New York at Buffalo, Buffalo, NY 14214, USA.
Abstract:
P2X(2) purinoceptors are cation-selective channels activated by ATP and its analogues. Using single channel measurements we studied the channel's selectivity for the alkali metal ions and organic monovalent cations NMDG(+), Tris(+), TMA(+), and TEA(+). The selectivity sequence for currents carried by alkali metal ions is: K(+) > Rb(+) > Cs(+) > Na(+) > Li(+), which is Eisenman sequence IV. This is different from the mobility sequence of the ions in free solution suggesting there is weak interaction between the ions and the channel interior. The relative conductance for alkali ions increases linearly in relation to the Stokes radius. The organic ions NMDG(+), Tris(+), TMA(+) and TEA(+) were virtually impermeant. The divalent ions (Mn(2+), Mg(2+), Ca(2+) and Ba(2+)) induced a fast block visible as a reduction in amplitude of the unitary currents. Using a single-site binding model, the divalent ions exhibited an equilibrium affinity sequence of Mn(2+) > Mg(2+) > Ca(2+) > Ba(2+).
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