Figure 9.
Differential modulation of ΔR-CFTR gating by cytoplasmic and pipette NO3−. (A) Cytoplasmic NO3− boosts the Po of ΔR-CFTR when the pipette is filled with NO3−-containing solution. (B) Single-channel kinetic analysis reveals: First, external NO3− has slight effects on gating parameters (∼12% increase of the Po compared with Fig. 5 B). Second, in the presence of pipette NO3−, similar gating modulations as described in Fig. 5 B were observed when cytoplasmic Cl− was replaced with NO3−, indicating that the major binding site for the gating effect of NO3− is located on the cytoplasmic side of the membrane. Po, τo, and τc are as follows: 0.48 ± 0.02, 403 ± 49 ms, and 404 ± 57 ms for Cl−; and 0.71 ± 0.02, 776 ± 94 ms, and 281 ± 29 ms for NO3− (n = 15). The error bars represent the SEM of the mean.