title: A novel intracellular K+/H+ antiporter related to Na+/H+ antiporters is important for K+ ion homeostasis in plants.
abstract: In this study we have identified the first plant K+/H+ exchanger, LeNHX2 from tomato (Lycopersicon esculentum Mill. cv. Moneymaker), which is a member of the intracellular NHX exchanger protein family. The LeNHX2 protein, belonging to a subfamily of plant NHX proteins closely related to the yeast NHX1 protein, is abundant in roots and stems and is induced in leaves by short term salt or abscisic acid treatment. LeNHX2 complements the salt- and hygromycin-sensitive phenotype caused by NHX1 gene disruption in yeast, but affects accumulation of K+ and not Na+ in intracellular compartments. The LeNHX2 protein co-localizes with Prevacuolar and Golgi markers in a linear sucrose gradient in both yeast and plants. A histidine-tagged version of this protein could be purified and was shown to catalyze K+/H+ exchange but only minor Na+/H+ exchange in vitro. These data indicate that proper functioning of the endomembrane system relies on the regulation of K+ and H+ homeostasis by K+/H+ exchangers.
authors.affiliation: Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, 18080-Granada, Spain. kev@eez.csic.es
authors.forename: Kees
authors.initials: K
authors.lastname: Venema
authors.forename: Andrés
authors.initials: A
authors.lastname: Belver
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Marin-Manzano
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Rodríguez-Rosales
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Donaire
mesh_terms: D000595:Amino Acid Sequence; D002458:Cell Fractionation; D006056:Golgi Apparatus / Q000378:metabolism; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D027961:Potassium-Hydrogen Antiporters; D029701:Saccharomyces cerevisiae Proteins; D017923:Sodium-Hydrogen Exchangers; D011188:Potassium