FIGURE 3.

Vacuolar anions affect the ATP-dependent block of AtALMT9-mediated chloride currents. A, normalized AtLMT9-mediated currents elicited by a voltage ramp from +60 to −160 mV in 1. 5 s (holding potential +60 mV) with a chloride-based cytosolic buffer in the presence (+ATP) or absence of 1 mm ATP_free. The vacuolar buffers contained 100 mm Cl⁻ (left panel; 100 mm Cl_cyt⁻ + 1 mm malate_cyt, 100 mm Cl_vac⁻) or malate (right panel;100 mm Cl_cyt⁻ + 1 mm malate_cyt, 100 mm malate_vac). B, fraction of unblocked current (I_ATP/I_ctrl; mean ± S.E., n = 4) plotted against the applied membrane potential in the presence of 100 mm Cl⁻ or 100 mm malate in the vacuolar buffer. Data were fitted with Equation 3 (“Experimental Procedures”; Table 1; dashed lines) yielding V_½ = −66 ± 1 mV (100 mm Cl_vac⁻) and V_½ = −124 ± 1 mV (100 mm malate_vac). Error bars denote S.E.