Voltage-dependent removal of sodium inactivation by N-bromoacetamide and pronase

When perfused internally through crayfish giant axons, pronase removed sodium inactivation more than three times as fast at -100 mV as compared with -30 mV. N-bromoacetamide, applied internally, removed sodium inactivation twice as fast at -100 mV as at -30 mV, and the relative rate of removal declined with membrane depolarization in proportion to steady-state sodium inactivation. We conclude that in the closed conformation the sodium inactivation gate is partially protected from destruction by N-bromoacetamide and pronase.