Nonconserved mutations of R190 in Slo2.1 induce constitutive channel activity and alter the sensitivity to NFA. (A) R190A current traces recorded at +40 mV before (control) and after treatment of oocytes with 1 mM NFA. (B) I-V relationships for R190A Slo2.1 channels determined in the presence and absence of 1 mM NFA (n = 5). Oocytes were recorded 2 d after injection of oocytes with 0.32 ng cRNA. (C) R190Q current traces recorded at +40 mV before (control) and after treatment of oocytes with 1 mM NFA. (D) I-V relationships for R190Q Slo2.1 channels determined in the presence and absence of 1 mM NFA (n = 8). Oocytes were recorded 2 d after injection of oocytes with 0.42 ng cRNA. (E) R190K Slo2.1 current traces recorded at +40 mV before (control) and after treatment of oocytes with 1 mM NFA. (F) I-V relationships for R190K Slo2.1 channels determined in the presence and absence of 1 mM NFA (n = 8). Oocytes were recorded 2 d after injection of oocytes with 0.84 ng cRNA. (G) 1 mM NFA does not activate R190E Slo2.1 currents recorded at +40 mV. Note that unlike the other R190 mutant channels, R190E channel currents are time independent in the absence of NFA. (H) NFA does not alter the I-V relationships for R190E Slo2.1 channels (n = 9). Oocytes were recorded 1 d after injection of oocytes with 0.84 ng cRNA.