A two-lane mechanism for selective biological ammonium transport

Gordon Williamson, Guila Tamburrino, Adriana Bizior, Mélanie Boeckstaens, Gaëtan Dias Mirandela, Marcus G Bage, Andrei Pisliakov, Callum M Ives, Eilidh Terras, Paul A Hoskisson, Anna Maria Marini, Ulrich Zachariae, Arnaud Javelle

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Abstract

The transport of charged molecules across biological membranes faces the dual problem of accommodating charges in a highly hydrophobic environment while maintaining selective substrate translocation. This has been the subject of a particular controversy for the exchange of ammonium across cellular membranes, an essential process in all domains of life. Ammonium transport is mediated by the ubiquitous Amt/Mep/Rh transporters that includes the human Rhesus factors. Here, using a combination of electrophysiology, yeast functional complementation and extended molecular dynamics simulations, we reveal a unique two-lane pathway for electrogenic NH4+ transport in two archetypal members of the family, the transporters AmtB from Escherichia coli and Rh50 from Nitrosomonas europaea. The pathway underpins a mechanism by which charged H+ and neutral NH3 are carried separately across the membrane after NH4+ deprotonation. This mechanism defines a new principle of achieving transport selectivity against competing ions in a biological transport process.
Original languageEnglish
Article numbere57183
Number of pages22
JournaleLife
Volume9
DOIs
Publication statusPublished - 14 Jul 2020

Keywords

  • charged molecules
  • biological membranes
  • Escherichia coli
  • Nitrosomonas europaea
  • transport selectivity
  • biological transport processes

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    Williamson, G., Tamburrino, G., Bizior, A., Boeckstaens, M., Dias Mirandela, G., Bage, M. G., Pisliakov, A., Ives, C. M., Terras, E., Hoskisson, P. A., Marini, A. M., Zachariae, U., & Javelle, A. (2020). A two-lane mechanism for selective biological ammonium transport. eLife, 9, [e57183]. https://doi.org/10.7554/eLife.57183