The lipid environment determines the activity of the Escherichia coli ammonium transporter AmtB

Gaetan Dias Mirandela, Giulia Tamburrino, Paul A. Hoskisson, Ulrich Zachariae, Arnaud Javelle (Lead / Corresponding author)

Research output: Contribution to journalArticle

6 Citations (Scopus)
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Abstract

The movement of ammonium across biologic membranes is a fundamental process in all living organ-isms and is mediated by the ubiquitous ammonium transporter/methylammonium permease/rhesus protein (Amt/Mep/Rh) family of transporters. Recent structural analysis and coupled mass spectrometry studies have shown that the Escherichia coli ammonium transporter AmtB specifically binds 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG). Upon POPG binding, several residues of AmtB undergo a small conformational change, which stabilizes the protein against unfolding. However, no studies have so far been conducted, to our knowledge, to explore whether POPG binding to AmtB has functional consequences. Here, we used an in vitro experimental assay with purified components, together with molecular dynamics simulations, to characterize the relation between POPG binding and AmtB activity. We show that the AmtB activity is electrogenic. Our results indicate that the activity, at the molecular level, of Amt in archaebacteria and eubacteria may differ. We also show that POPG is an important cofactor for AmtB activity and that, in the absence of POPG, AmtB cannot complete the full translocation cycle. Furthermore, our simulations reveal previously undiscovered POPG binding sites on the intracellular side of the lipid bilayer between the AmtB subunits. Possible molecular mechanisms explaining the functional role of POPG are discussed.
Original languageEnglish
Pages (from-to)1989-1999
Number of pages11
JournalFASEB Journal
Volume33
Issue number2
Early online date13 Sep 2018
DOIs
Publication statusPublished - Feb 2019

Keywords

  • Amt/Mep/Rh
  • Molecular dynamics simulation
  • Protein-lipids interaction
  • SSME

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