Ligand-induced conformational dynamics of the Escherichia coli Na⁺/H⁺ antiporter NhaA revealed by hydrogen/deuterium exchange mass spectrometry

Na⁺/H⁺ antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life and play an essential role in cellular ion homeostasis. The NhaA crystal structure of Escherichia coli has become the paradigm for this class of secondary active transporters. However, structur...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2017-10, Vol.114 (44), p.11691-11696
Main Authors: Eisinger, Martin Lorenz, Dörrbaum, Aline Ricarda, Michel, Hartmut, Padan, Etana, Langer, Julian David
Format: Article
Language:English
Subjects:
Binding sites
Biological Sciences
Cellular structure
Crystal structure
Deuterium
E coli
Escherichia coli
Homeostasis
Ligands
Mass spectrometry
Mass spectroscopy
Membrane proteins
Na+/H+-exchanging ATPase
pH effects
Proteins
Scientific imaging
Spectroscopy
Translocation
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Summary:Na⁺/H⁺ antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life and play an essential role in cellular ion homeostasis. The NhaA crystal structure of Escherichia coli has become the paradigm for this class of secondary active transporters. However, structural data are only available at low pH, where NhaA is inactive. Here, we adapted hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to analyze conformational changes in NhaA upon Li⁺ binding at physiological pH. Our analysis revealed a global conformational change in NhaA with two sets of movements around an immobile binding site. Based on these results, we propose a model for the ion translocation mechanism that explains previously controversial data for this antiporter. Furthermore, these findings contribute to our understanding of related human transporters that have been linked to various diseases.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1703422114