Figure 4. The blocker glibenclamide... | Rockefeller University Press

Figure 4.

$Figure 4. The blocker glibenclamide protects engineered cysteine residues from modification by MTSES−. (A) In an inside-out patch containing thousands of cysless/W1145C-CFTR channels, MTSES− was first (indicated by orange lines) applied in the presence of 200 µM glibenclamide (yielding 77% steady-state blockade), and then (red lines) in the absence of glibenclamide after the chemical modification was reversed by the reducing reagent, DTT. (B) Comparison of modification time courses with or without glibenclamide. Portions of the current trace from A were normalized in current amplitude and fitted with single-exponential functions, yielding the modification time constant (τ), as indicated in the figure. This comparison shows that modification rate with glibenclamide (orange) is 24% of that without glibenclamide (red). Thus, the presence of glibenclamide almost completely protects the cysteine against modification, given that the fraction of block is 77%. (C) The bars originating at 1 and ending at a value of <1 on the logarithmic axis correspond to the decrease in the modification rate produced by the blocker glibenclamide. The relative modification rate of blocked channels compared with unblocked ones was corrected for the fraction of block (see Materials and methods).$

The blocker glibenclamide protects engineered cysteine residues from modification by MTSES⁻. (A) In an inside-out patch containing thousands of cysless/W1145C-CFTR channels, MTSES⁻ was first (indicated by orange lines) applied in the presence of 200 µM glibenclamide (yielding 77% steady-state blockade), and then (red lines) in the absence of glibenclamide after the chemical modification was reversed by the reducing reagent, DTT. (B) Comparison of modification time courses with or without glibenclamide. Portions of the current trace from A were normalized in current amplitude and fitted with single-exponential functions, yielding the modification time constant (τ), as indicated in the figure. This comparison shows that modification rate with glibenclamide (orange) is 24% of that without glibenclamide (red). Thus, the presence of glibenclamide almost completely protects the cysteine against modification, given that the fraction of block is 77%. (C) The bars originating at 1 and ending at a value of <1 on the logarithmic axis correspond to the decrease in the modification rate produced by the blocker glibenclamide. The relative modification rate of blocked channels compared with unblocked ones was corrected for the fraction of block (see Materials and methods).