Fig. 3.
Thiocyanate block of selectivity filter variants. (A) Example current-voltage relationships for PKA-phosphorylated CFTR variants with different mole fractions of thiocyanate. The patch pipette contained 150 mM chloride, and the perfusion solution contained a mixture of chloride and thiocyanate. Three mM ATP was used in the perfusion solution. Membrane potentials are indicated using physiological convention. Corresponding voltage families are in SI Appendix, Fig. S4. (B) Thiocyanate block of CFTR conductance. Relative reduction of conduction was measured at the reversal potential as a function of the mole fraction of monovalent anion that was thiocyanate (xSCN). The apparent anomalous mole fraction effect of the T338A variant was not statistically significant (P = 0.21 between xSCN = 0.5 and xSCN = 1 by Student’s two-tailed t test). Representative voltage families for xSCN = 1 are in SI Appendix, Fig. S3 and for xSCN < 1 are in SI Appendix, Fig. S4. Data represent means and SE for 4 to 10 patches.