Figure 1.

Single channel behavior in WT-CFTR is different in high and low PKA concentration. Representative single-channel current traces are shown for WT-CFTR in low PKA (A, 6.4 U/ml) and high PKA (B, 127.6 U/ml), from one inside-out membrane patch excised from Xenopus oocytes, with symmetrical 150 mM Cl⁻ solution in the presence of 1 mM MgATP. All traces were recorded at Vm = -100 mV. c = closed state; f = full open state. All-points amplitude histograms are shown in the right panels, where solid lines are fit results to a Gaussian function. Single channel amplitude (C), open probability (n = 4) (D), and mean burst duration (E) of WT-CFTR in low and high PKA conditions are shown. n = 5. (F) Representative macropatch currents of WT-CFTR recorded in inside-out mode with symmetrical 150 mM Cl⁻ solution under the following experimental conditions: channels were fully activated in 1 mM MgATP + 6.4 U/ml PKA followed by 1 mM MgATP + 127.6 U/ml PKA. A voltage-ramp protocol described in the Methods section was applied every 5 s. ▼, 10 µM CFTR_inh172.