Effects of 1 mM MTSET⁺ (ET⁺) and MTSES⁻ (ES⁻) on WT-, D110C-, E116C-, R117C-, and R334C-CFTR. Representative whole-cell TEVC current traces were recorded at V_M = −60 mV in ND96 solution in cells expressing CFTR with the β₂AR (see Materials and methods). After activation with 10 µM ISO, oocytes were exposed to 1 mM ET⁺ or ES⁻ in the continuing presence of ISO. Summary data for all mutants tested under the same conditions are shown below the sample current traces. Some error bars are too small to view. *, P < 0.05 compared with WT-CFTR. n = 4–6. Mean ± SEM is shown.