Figure 8.

Conductivity and selectivity properties of the TaALMT1-mediated currents. A, Effect of {Cl⁻}_o on the conductance (G) of the inward (left) and outward (right) currents in TaALMT1-expressing (circles) and control (triangles) cells. The conductance was estimated by linear regression of the six most positive test potentials from the I/V relationships shown in Figure 7B. B, E_rev from TaALMT1-expressing (circles) and control (triangles) cells preloaded with malate (black symbols) or water (white symbols), plotted as a function of the E_Cl⁻, assuming an internal Cl⁻ activity of 60 mm. E_rev values correspond to those shown in Figure 7C. The line represents the theoretical values when E_Cl⁻ equals E_rev. C, Shift in the observed E_rev plotted as a function of the overall change in {Cl⁻}_o. The shift in the observed E_rev (E_rev − E_rev^ref) was defined as the difference between the recorded E_rev at a given {Cl⁻}_o and the recorded E_rev at the highest {Cl⁻}_o (i.e. E_rev^ref). Likewise, the decrease in {Cl⁻}_o was defined as the differences between the highest {Cl⁻}_o tested (i.e. 75 mm) and that present in the bath solution in each case. The lines represent the theoretical changes in E_rev expected by decreasing {Cl⁻}_o at a given constant P_mal²⁻/P_Cl⁻ value (as indicated). The theoretical values were calculated from expected shifts in the net current (i.e. the sum of I_Cl⁻ and I_mal²⁻) predicted from the GHK current equation (Equation 14.5 in Hille, 2001), as {Cl⁻}_o varied and {Cl⁻}_i and {mal²⁻}_i remained constant at 60 and 4.5 mm, respectively.