Fig. 6.

Current–voltage curves for the plasma membrane H⁺-ATPase (above) and the tonoplast H⁺-VATPase and H⁺-PPase (below) taken at 2 h into the light period in each case. Curves for the ost2 mutant are shown in gray. At the free-running voltage, the model predicts roughly a 20% increase in H⁺-ATPase current at the plasma membrane, despite the reduced substrate (H⁺) concentration. It also predicted roughly a 50% decrease in H⁺ transport into the vacuole at the free-running voltage via the two tonoplast pumps in ost2.