Mutagenesis scan to identify amino acid residues involved in high-affinity Zn²⁺ inhibition and effect of Zn²⁺ chelation on ASIC current mediated by various mutant ASIC1a channels expressed in CHO cells. A, Alignment of ASIC1a, ASIC1β, ASIC2a, and ASIC3 identifies potential Zn²⁺ interaction sites (C, E, H, and K residues) that were present in ASIC1a but not conserved at homologous positions in ASIC1β, ASIC2a, and ASIC3. B, Representative traces showing TPEN potentiation of ASIC current mediated by WT, C61A, H173A, E97A, E123A, and K133R mutant ASIC1a channels. Mutation of K133 to R eliminated TPEN potentiation of the ASIC1a current. C, Summary data showing relative increase in the amplitude of ASIC current mediated by WT ASIC1a and different mutant channels by bath application of 10 μm TPEN; n = 5-32; ^**p < 0.01.