Alanine- and cysteine-scanning mutagenesis of the V47–V61 rP2X4R segment.

In this and Table 2, the potency is expressed as the ATP concentration producing 50% of the maximal response (EC50), and the efficacy as the maximum induced current (Imax) in response to 100 µM ATP. The Imax data are expressed as the mean ± SEM from 12–40 measurements per mutant and 96 measurements from the wild type (WT) receptor. n.d., not determined; n.f., nonfunctional; **p<0.01, between mutant and WT (used for Imax measurements); *p<0.05 between mutant and WT (used for EC50 estimation).