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Title

Mutants of the Arabidopsis thaliana Cation/H+ Antiporter AtNHX1 Conferring Increased Salt Tolerance in Yeast . The Endosome/prevacuolar compartment is a target for salt toxicity

AuthorsHernández, Agustín CSIC ORCID; Jiang, Xingyu CSIC; Cubero, Beatriz CSIC ; Nieto, Pedro M. CSIC ORCID ; Bressan, Ray A.; Hasegawa, Paul M.; Pardo, José M. CSIC ORCID
KeywordsCation Transport Proteins
Structure
Sodium_Hydrogen Antiporter
Biogenesis
Arabidopsis proteins
Magnetic Resonance Spectroscopy
Issue Date22-May-2009
PublisherAmerican Society for Biochemistry and Molecular Biology
CitationThe Journal of Biological Chemistry 284 (21): 14276-14285 (2009)
AbstractMutants of the plant cation/H+ antiporter AtNHX1 that confer greater halotolerance were generated by random mutagenesis and selected in yeast by phenotypic complementation. The amino acid substitutions that were selected were conservative and occurred in the second half of the membrane-associated N terminus. AtNHX1 complemented the lack of endogenous ScNHX1 in endosomal protein trafficking assays. Growth enhancement on hygromycin B and vanadate media agreed with a generally improved endosomal/prevacuolar function of the mutated proteins. In vivo measurements by 31P NMR revealed that wild-type and mutant AtNHX1 transporters did not affect cytosolic or vacuolar pH. Surprisingly, when yeast cells were challenged with lithium, a tracer for sodium, the main effect of the mutations in AtNHX1 was a reduction in the amount of compartmentalized lithium. When purified and reconstituted into proteoliposomes or assayed in intact vacuoles isolated from yeast cells, a representative mutant transporter (V318I) showed a greater cation discrimination favoring potassium transport over that of sodium or lithium. Together, our data suggest that the endosome/prevacuolar compartment is a target for salt toxicity. Poisoning by toxic cations in the endosome/prevacuolar compartment is detrimental for cell functions, but it can be alleviated by improving the discrimination of transported alkali cations by the resident cation/H+ antiporter.
Description10 páginas, 8 figuras, 1 tabla.
Publisher version (URL)http://dx.doi.org/10.1074/jbc.M806203200
URIhttp://hdl.handle.net/10261/37498
DOI10.1074/jbc.M806203200
ISSN0021-9258
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