Whole-cell patch-clamp analysis of mouse fibroblasts transfected with wild-type and mutant forms of the maxi-K channel. Current density recordings for Ltk- cells transfected with (A) WT, (B) mutant F1012A, (C) mutant Y1007A, F1012A and (D) mutant Y1007A, F1012A, Y1015A maxi-K channel constructs. (E) Bar graph data summarizes and compares the mean current densities generated by cells transfected with the indicated maxi-K channel construct. Cells transfected with mutant F1012A, mutant Y1007A, F1012A and mutant Y1007A, F1012A, Y1015A exhibited 53%, 49% and 59% decreases in current density, respectively, in comparison to cells transfected with the WT construct. (*) indicate statistically significant differences between currents generated in cells transfected with each mutant maxi-K channel construct versus cells transfected with the WT construct (p < 0.05). Data shown are the mean values for 10 (WT, mutant F1012A, mutant Y1007A, F1012A) and 7 (mutant Y1007A, F1012A, Y1015A) independent experiments ± standard error.