Figure 5
Hd P2X receptor currents are inhibited by zinc and copper. Two-electrode voltage clamp recordings were made from Xenopus oocytes expressing HdP2X at a holding potential of -60 mV. A. Concentration response curves for 100 μM ATP (~EC80) in the presence of varying concentrations of zinc (open circles) (n = 6) and copper (closed squares) (n = 6). B. Effects of single and double point mutations on inhibition by 100 μM zinc and copper. Mean currents are normalised to the 100 μM ATP response in the absence of zinc or copper for wild type and mutant receptors (n = 7). C. ATP concentration response curves for histidine point mutations (n = 7). For each single and double histidine mutation no significant change in ATP sensitivity was observed suggesting that mutation had not resulted in gross changes in receptor conformation. The triple histidine mutation H232A/H252A/H306A produced a non functional channel and so could not be studied.