Figure 4.

Modification of cysteines in the inner vestibule of the pore by intracellular MTS reagents. (A and B) Example leak-subtracted macroscopic I-V relationships for different CFTR variants (in a cys-less background), using symmetrical high (154-mM) Cl⁻ concentrations, after maximal channel activation with 5–10 nM PKA, 1 mM ATP, and 2 mM PPi. Currents were recorded before (control) and after the addition of 200 µM MTSES (A) or 2 mM MTSET (B) to the intracellular (bath) solution. (C) Mean effect of MTSES (filled bars) or MTSET (open bars) on macroscopic current amplitude at −80 mV (left) and +80 mV (right). Asterisks indicate a significant difference from cys-less (P < 0.05). Daggers indicate a significant difference from the same treatment at −80 mV (P < 0.05, paired t test). Mean of data from 3–10 patches.