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Functional Analysis of the Na(+),K(+)/H(+) Antiporter PeNHX3 from the Tree Halophyte Populus euphratica in Yeast by Model-Guided Mutagenesis

Na(+),K(+)/H(+) antiporters are H(+)-coupled cotransporters that are crucial for cellular homeostasis. Populus euphratica, a well-known tree halophyte, contains six Na(+)/H(+) antiporter genes (PeNHX1-6) that have been shown to function in salt tolerance. However, the catalytic mechanisms governing...

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Detalles Bibliográficos
Autores principales: Wang, Liguang, Feng, Xueying, Zhao, Hong, Wang, Lidong, An, Lizhe, Qiu, Quan-Sheng
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122410/
https://www.ncbi.nlm.nih.gov/pubmed/25093858
http://dx.doi.org/10.1371/journal.pone.0104147
Descripción
Sumario:Na(+),K(+)/H(+) antiporters are H(+)-coupled cotransporters that are crucial for cellular homeostasis. Populus euphratica, a well-known tree halophyte, contains six Na(+)/H(+) antiporter genes (PeNHX1-6) that have been shown to function in salt tolerance. However, the catalytic mechanisms governing their ion transport remain largely unknown. Using the crystal structure of the Na(+)/H(+) antiporter from the Escherichia coli (EcNhaA) as a template, we built the three-dimensional structure of PeNHX3 from P. euphratica. The PeNHX3 model displays the typical TM4-TM11 assembly that is critical for ion binding and translocation. The PeNHX3 structure follows the ‘positive-inside’ rule and exhibits a typical physicochemical property of the transporter proteins. Four conserved residues, including Tyr149, Asn187, Asp188, and Arg356, are indentified in the TM4-TM11 assembly region of PeNHX3. Mutagenesis analysis showed that these reserved residues were essential for the function of PeNHX3: Asn187 and Asp188 (forming a ND motif) controlled ion binding and translocation, and Tyr149 and Arg356 compensated helix dipoles in the TM4-TM11 assembly. PeNHX3 mediated Na(+), K(+) and Li(+) transport in a yeast growth assay. Domain-switch analysis shows that TM11 is crucial to Li(+) transport. The novel features of PeNHX3 in ion binding and translocation are discussed.