Figure 2 Whole‐cell patch clamp analysis of Cl⁻ currents induced by wild‐type hBest1 and the Q293H mutation. Q293H mutation blocked the normal function of hBest1 as Ca²⁺‐activated Cl⁻ channel in transfected HEK‐293 cells. The voltage clamp protocol is shown. (A–C) Representative current traces from cells transfected with wild‐type (WT), Q293H mutant and WT+Q293H hBest1, respectively. (D) Averaged current–voltage (I–V) relations for WT (n = 13), Q293H (n = 7) and cotransfection of WT+ Q293H (n = 12). (E) Current amplitudes at −100 and +100 mV from the above recordings and those from cells transfected with EGFP alone (n = 5). Dots indicate data of individual cells. Whole‐cell recording from transfected HEK‐293 cells showed that the Q293H mutant channel is non‐functional when transfected alone, and considerably inhibited the wild‐type current when cotransfected with WT hBest1 (p<0.05, two‐tailed t test).