Fig. 1: Potassium dependent activation of AtHAK5.

A Representative original currents (black trace) at −120 mV of an oocyte co-expressing AtAKT1 and CIPK23/CBL1 at pH 4.5 in the presence of different potassium concentrations (2 mM, 20 µM or nominally 0 µM K⁺). Simultaneously, the bath K⁺ concentration was recorded via K⁺-selective electrodes (representative trace in red). B Representative K⁺-induced currents at −120 mV of either control oocytes or oocytes expressing either AtHAK5 alone or co-expressing AtHAK5 together with CIPK23/CBL1. C Quantification of K⁺-induced peak currents at −120 mV of either control oocytes (n = 4 experiments) or oocytes expressing AtHAK5 in the presence or absence of CIPK23/CBL1 (n = 5 experiments). D Measurement of original current traces (in black) at −120 mV in oocytes co-expressing AtHAK5 and CIPK23/CBL1 at pH 4.5 in the presence of different potassium concentrations (2 mM, 20 µM or nominally 0 µM K⁺). In the bath a K⁺-selective electrode simultaneously recorded the apparent K⁺ concentration (red trace; Representative traces are shown). E Normalized whole-oocyte K⁺-induced peak currents (ΔI_peak) (n = 3 experiments, mean ± SD) or steady-state currents (ΔI_SS) (n = 4 experiments, mean ± SEM) at −120 mV at pH4.5 are plotted against the applied K⁺-concentration. K_m (K⁺) was calculated by fitting ΔI_peak with a Michaelis-Menten equation. The modified Michaelis-Menten function used to fit ΔI_SS is described in the methods section.