Modification of A43C residues by bBBr occurs at voltages that favor channel closure. (A) Macroscopic currents attributable to A43C channels are irreversibly decreased when exposed to bBBr during a voltage paradigm, steps between 0 and −90 mV, which elicits gating transitions between the open (0 mV) and either loop- and/or Vj-gating closed states (−90 mV). (B) Application of bBBr during a voltage paradigm, steps from 0 to 30 mV, which favors population of the open-channel state, has no effect on A43C macroscopic currents. The central bar in both panels indicates the time and duration for which the bath solution containing 500 µM TCEP was exchanged with the same bath solution containing 1 mM bBBr and subsequently washed with TCEP containing bath solution.
