Fig. 1.
NO selectively inactivates IK,in. Voltage-clamp recordings from an intact Vicia guard cell are shown. (Inset) Steady-state current–voltage curves determined from voltage-clamp steps before (•), after 2 min of exposure to 10 μM SNAP (▴), and after 6 min of washing in buffer-SNAP (○). K+-channel currents were obtained by subtracting instantaneous current from steady-state current at each voltage. Data for IK,in and IK,out were fitted jointly (solid lines) to common Boltzmann functions (20, 24) with the voltage sensitivity parameter V1/2, the voltage giving half-maximal conductance, free to vary between curves. Values for V1/2 (IK,in): -NO, -173 ± 4 mV; +NO, -192 ± 9 mV. (Inset) Current traces for IK,out (Left) and IK,in (Right) before (Middle) and during (Bottom) NO treatment. Zero current is indicated on the left. Voltage protocols (Top) of steps between -200 and +50 mV from holding voltage of -100 mV are shown. (Scale: horizontal, 2 s; vertical, 1 nA.)