The double H325E+G331K and H325C+G331K mutants manifest two permeation pathways within the same channel. A) Current-voltage relationship for H325E+G331K and H235C+G331K double mutants display inward current in the voltage range where maximum inward rectification is observed in N.at-K
3.2. However, at more depolarizing voltages the current increases in a pattern typical for a voltage-activated delayed rectifier channel. B) Channels were treated with 10 mM TEA for 10 min. to block the delayed rectifier component of the dual phenotype channels. Pharmacological block was calculated for each individual experiment as % control current (where the control is ND96) at two voltages; -140 mV (filled bars) representing the omega current, and +70 mV (patterned bars) representing the delayed rectifier component. The delayed rectifier component (+70 mV current) of H325C+G331K and H325E+G331K mutants was blocked by 10 mM TEA while the wild-type was unaffected (n = 6, error bars denote s.e.m.). The current through the gating pore (-140 mV) remained unaffected in both mutants and the wild-type channel.