Figure 2.

Initial rates of Rb⁺ uptake in yeast cells expressing HAK5, CIPK23, and CBL1. Cells of trk1 trk2 genotype transformed with the empty vector (EV; black squares), CIPK23/CBL1 (white triangles), HAK5 (black triangles), HAK5/CIPK23 (white circles), or HAK5/CIPK23/CBL1 (black circles) were grown overnight in AP medium supplemented with 5 mm K⁺. After 6 h of K⁺ starvation, cells were suspended in assay buffer supplemented with different Rb⁺ concentrations. Initial rates of Rb⁺ uptake were determined and plotted against the corresponding Rb⁺ concentrations. Data were fitted to Michaelis-Menten equations and the K_m and V_max values calculated. Data represent the average of at least three repetitions, and error bars denote se.