Figure 2.

SC current-voltage (I/V) relationships of wt VDAC-1. (A) Computational I/V relationship of mVDAC-1 simulated in 0.5 M NaCl, and at ion imbalances (Δq) from 2 to 14 (only POPE is shown; for POPC results, see Fig. S1 C). Each I/V data point (circles) is colored according to selectivity, defined as the permeation ratio between chloride and sodium. The mean conductance values (± SE) of 1.63 (± 0.08) and 1.96 (± 0.11) nS are shown as red lines for the negative and positive voltages, respectively. (B) Voltage-dependent pseudo-open probability of a single mVDAC-1 channel. Each data point represents the average probability (± SD) of finding the channel at a conductance value >1.4 and 1.5 nS. The I/V data were binned every 150 mV from −500 to 500 mV and excluded the voltage range from −50 to 50 mV. (C) I/V relationship of hVDAC-1 inserted in a solvent-free DPhPC/cholesterol (9:1) membrane bathed in 1 M KCl, 1 mM CaCl₂, and 5 mM HEPES, pH 7.4. The voltage-ramp data (blue dots) were taken after the insertion of a single hVDAC-1 channel was proven by a mean conductance value of 4–4.5 nS. The dashed lines mark the 3 and 2 nS conductance values of the most frequent “closed” subconducting states visited by hVDAC-1 ($G_{\text{S1}}$ and $G_{\text{S}2}$). The red line shows the mean conductance value averaged over 185 voltage ramps, which was 4.2 and 4.5 nS (mean ± SE = 0.006) in the negative and positive voltage sides, respectively. (D) Voltage-dependent open probability of an SC hVDAC-1 for the voltage ramps shown in (C). To see this figure in color, go online.