R117, E116, and D110 do not interact with each other locally to affect open pore architecture of CFTR. (A) Representative single-channel currents of R117E/E116R-, R117E/D110R-, and R117E/E116R/D110R-CFTR and corresponding all-points amplitude histograms recorded under the same conditions as Fig. 2 A. (B) Mean burst duration of WT-CFTR and the three compound mutants. #, P < 0.001 compared with WT-CFTR. n = 4–6 for all mutants. (C) Mean single-channel amplitudes of WT-, R117E/E116R-, R117E/D110R-, and R117E/E116R/D110R-CFTR. *, P < 0.05 compared with WT-CFTR. Mean ± SEM is shown.