title: Sodium or potassium efflux ATPase a fungal, bryophyte, and protozoal ATPase.
abstract: The K(+) and Na(+) concentrations in living cells are strictly regulated at almost constant concentrations, high for K(+) and low for Na(+). Because these concentrations correspond to influx-efflux steady states, K(+) and Na(+) effluxes and the transporters involved play a central role in the physiology of cells, especially in environments with high Na(+) concentrations where a high Na(+) influx may be the rule. In eukaryotic cells two P-type ATPases are crucial in these homeostatic processes, the Na,K-ATPase of animal cells and the H(+)-ATPase of fungi and plants. In fungi, a third P-type ATPase, the ENA ATPase, was discovered nineteen years ago. Although for many years it was considered to be exclusively a fungal enzyme, it is now known to be present in bryophytes and protozoa. Structurally, the ENA (from exitus natru: exit of sodium) ATPase is very similar to the sarco/endoplasmic reticulum Ca(2+) (SERCA) ATPase, and it probably exchanges Na(+) (or K(+)) for H(+). The same exchange is mediated by Na(+) (or K(+))/H(+) antiporters. However, in eukaryotic cells these antiporters are electroneutral and their function depends on a DeltapH across the plasma membrane. Therefore, the current notion is that the ENA ATPase is necessary at high external pH values, where the antiporters cannot mediate uphill Na(+) efflux. This occurs in some fungal environments and at some points of protozoa parasitic cycles, which makes the ENA ATPase a possible target for controlling fungal and protozoan parasites. Another technological application of the ENA ATPase is the improvement of salt tolerance in flowering plants.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Campus Montegancedo, carretera M-40, km 37.7, 28223-Pozuelo de Alarcón, Madrid, Spain. alonso.rodriguez@upm.es
authors.forename: Alonso
authors.initials: A
authors.lastname: Rodríguez-Navarro
authors.forename: Begoña
authors.initials: B
authors.lastname: Benito
mesh_terms: D000595:Amino Acid Sequence; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D010940:Plant Proteins; D015800:Protozoan Proteins; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium