Figure 1.

Activity of the yeast vacuolar cation channel is modulated by membrane voltage and cytosolic redox state. A, Single channel currents from the yeast tonoplast in an excised membrane patch with 100 mm K⁺ in pipette and bath. The bath (cytosolic side) contained 10 μm Ca²⁺. The solid line indicates the baseline with all channels closed, and the dashed lines mark the open states with the corresponding membrane voltages to the right of each trace. B, Continuous current recording (top row) from an excised tonoplast patch demonstrating activation of at least nine channels by addition of 1 mm NADH to the bath (cytosolic) solution (150 mm KCl, 50 μm Ca²⁺, V_m = −40 mV). Baseline with all channels closed is marked by the solid line; open channel levels are indicated by the dashed lines. Two segments at higher time resolution are shown in the second and bottom rows, respectively. All data were filtered at 400 Hz and sampled at 1 kHz. C, Whole-vacuole currents from the yvc1 deletion strain in response to 2.5-s voltage pulses in the range of ±100 mV in 20-mV increments with ionic conditions as in A, but with 100 μm Ca²⁺ in the bath (cytosolic side). Data were filtered at 100 Hz and sampled at 1 kHz.