An asparagine residue regulating conductance through P2X₂ receptor/channels

Single channel currents were recorded from Xenopus oocytes expressing wild-type and mutated P2X₂ receptors. When 100 mM Na⁺ was used as the permeant cation, unitary currents of about 80 pS were recorded from the oocyte expressing the wild-type channels. The single channel conductance was roughly halved when Asn³³³ was replaced by lie (N333I). A similar decrease in single channel currents was also observed when 100 mM Li⁺ or Cs⁺ was used as the permeant cation. With two other mutants, in which Asp³¹⁵ was replaced by Val (D315V) or Tyr³³⁰ was replaced by Ile (T333I), single channel conductance was almost the same as that of the wild-type channels. The results suggest that Asn³³³, which is believed to be involved in the channel pore, plays an essential role in ion transport through P2X₂ receptor/channels.