NhaA antiporter functions using 10 helices, and an additional 2 contribute to assembly/stability

Etana Padan*, Tsafi Danieli, Yael Keren, Dudu Alkoby, Gal Masrati, Turkan Haliloglu, Nir Ben-Tal, Abraham Rimon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The Escherichia coli Na+/H+ antiporter (Ec-NhaA) is the best-characterized of all pH-regulated Na+/H+ exchangers that control cellular Na+ and H+ homeostasis. Ec-NhaA has 12 helices, 2 of which (VI and VII) are absent from other antiporters that share the Ec-NhaA structural fold. This α-hairpin is located in the dimer interface of the Ec-NhaA homodimer together with a β-sheet. Here we examine computationally and experimentally the role of the α-hairpin in the stability, dimerization, transport, and pH regulation of Ec-NhaA. Evolutionary analysis (ConSurf) indicates that the VI-VII helical hairpin is much less conserved than the remaining transmembrane region. Moreover, normal mode analysis also shows that intact NhaA and a variant, deleted of the α-hairpin, share similar dynamics, suggesting that the structure may be dispensable. Thus, two truncated Ec-NhaA mutants were constructed, one deleted of the α-hairpin and another also lacking the β-sheet. The mutants were studied at physiological pH in the membrane and in detergent micelles. The findings demonstrate that the truncated mutants retain significant activity and regulatory properties but are defective in the assembly/stability of the Ec-NhaA dimer.

Original languageAmerican English
Pages (from-to)E5575-E5582
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number41
DOIs
StatePublished - 13 Oct 2015

Keywords

  • ConSurf
  • Elastic network model
  • Helices truncation
  • Na/H antiporter/NhaA
  • Transport protein

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