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Figure 3. Altered Conductance and Affinity in the DmHKT1 S84G Mutant.(A) Steady-state currents (Iss) of DmHKT1 wild-type (WT) and S84G-expressing oocytes measured at −140 mV and in 100 mM of the indicated cations (n = 4, mean ± SD).(B) Steady-state currents (Iss) of DmHKT1 S84G at −140 mV were monitored in and plotted against increasing K+ concentrations up to 100 mM (please note different scaling). The current response reached a maximum at 50 mM KCl and with higher concentrations, the K+ inward currents declined. Currents up to 50 mM K+ could be fitted with the Michaelis–Menten equation revealing a Km value of 9.01 ± 1.99 mM K+ (n = 5, mean ± SD).(C) By applying 10 mM NaCl, 10 mM KCl, and a combination of 10 mM of each cation at −140 mV, S84G-mediated currents under combined ion conditions were the sum of the current responses to each cation alone (n = 5, mean ± SD).(D) Steady-state currents (Iss) of the WT DmHKT1 and the mutant S84G were monitored in bath solutions containing 10 mM KCl and a stepwise increase in sodium concentrations. WT-mediated currents could be fitted with the Michaelis–Menten equation, whereas the current response of S84G proceeded in a linear-dependent manner (n ≥ 4, mean ± SD).(E) In inverse experiments, steady-state currents (Iss) of the WT and the mutant S84G were measured in 10 mM NaCl and a stepwise increase in potassium concentrations (n ≥ 4, mean ± SD). The resulting currents showed behavior opposite to that shown in (D).(F) The AMFE of S84G-expressing cells (n = 4, mean ± SD) analyzed in increased Na+ concentrations, supplemented with K+ to a final concentration of 50 mM. To maintain the ionic strength, 50 mM LiCl was used. The steady-state currents (Iss) at −140 mV were plotted against the sodium concentration. Image published in: Böhm J et al. (2016) © 2016 The Authors. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives license Larger Image Printer Friendly View

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