Cation Fungal Homeostasis

Maintenance of the appropriate intracellular concentrations of monovalent cations, mostly potassium and sodium, is a requirement for living cells, and this is particularly relevant in cells that, like unicellular fungi, are directly exposed to a changing environment. These organisms are endowed with a variety of cation influx and efflux systems. Import of potassium, which is accumulated intracellularly, is achieved by means of at least three different kind of transporters, whereas removal of the surplus of sodium (a relatively toxic cation) is accomplished by a combination of Na + -ATPases and antiporters. In addition, toxic cations can be confined in intracellular organelles, such as the vacuole, with the aid of intracellular transporters. Fine regulation of these elements allows a relatively constant ionic intracellular composition in spite of sudden changes in the external medium.