The mechanisms mediating potassium uptake in S. cerevisiae are still unresolved. Potassium is accumulated by yeast cells against a very wide range of concentration gradients. While intracellular potassium reaches concentrations of around 200 to 300 mM, extracellular potassium can be in the low mM or micromolar range. Therefore, yeast cells have to adapt to changing environmental conditions, and the mechanism of transport may not be the same under different growth conditions.