Figure 7. Comparison of current amplitudes from mutant and WT mBest2 Cl⁻ channels.

Mean current densities from non-transfected cells (HEK nt) and cells transfected with EGFP and WT or mutated mBest2. The intracellular pipette solution contained nominally 0 (white bar) or 22 µM free Ca²⁺ (black bar). Data are shown as mean value±standard error of the mean. Each data represents the mean of at least five cells. Control experiments with non-transfected HEK-293 cells did not show any appreciable current. Mean current densities in the presence of 22 µM free Ca²⁺ of WT, E306A and D312A were significantly higher than those in nominally 0 Ca²⁺ (P<0.02; N = 5–13), whereas currents at the two Ca²⁺ levels were not statistically different for D301A, D304A and D304A+E306A (P>0.05, N = 5–20). Currents in the presence of 22 µM free Ca²⁺ of D301A, D304A, and D304A+E306A were substantially decreased compared with WT (P<0.002 for each group, N = 5–20). E306A had a mean value not significantly different from WT (P = 0.5; N = 7–8). D312A showed a current increase compared to WT both in the absence (P = 0.03; N = 9–13) and in the presence of Ca²⁺ (P = 0.003; N = 6–8).