Acidic residues contribute to metal sensitivity of mSlo1 and other voltage-gated channels. (A) Multiple sequence alignment of voltage sensor domain from mSlo1, Kv channels (Shaker, Kv1.2, and Kv2.1), dEAG, and hERG, and other voltage-gated channels (Nav1.4, Nav1.5, Cav1.4, Cav3.2 Domain IV) (based on Liu et al., 2003; Long et al., 2007). Putative transmembrane segments are indicated by solid bars (Long et al., 2007). Charged residues that are highly conserved in mSlo1 and other voltage-gated channels are in red (acidic) or blue (basic). Sites that were mutated in mSlo1 are highlighted yellow with positions labeled. Putative metal coordinating residues in mSlo1, dERG, and hERG are indicated by boxes. (B) Dose–response relations (G_K at +260 mV) fit by Hill equations for D153K (▪, IC₅₀ = 16.7 μM, n_H = 1.0) and D153H (▴, IC₅₀ = 0.26 μM, n_H = 0.73) (5 μM [Ca²⁺]_i). Dashed curve represents fit to WT data from Fig. 5 C. (C) The dose–response relation (G_K at +160 mV) for D186A (•, IC₅₀ = 2.53 μM, n_H = 0.97), D186H (▴, IC₅₀ = 2.82 μM, n_H = 0.95) (1 μM [Ca²⁺]_i). (D) The dose–response relations (G_K at +240 mV) for D133A (•, IC₅₀ = 56.5 μM, n_H = 0.97), D133C (<, IC₅₀ = 1.5 μM, n_H = 0.74) and D133H (▴, IC₅₀ = 0.73 μM, n_H = 0.63) (0 [Ca²⁺]_i).