A two-lane mechanism for selective biological ammonium transport
- University of Strathclyde, United Kingdom
- University of Dundee, United Kingdom
- Université Libre de Bruxelles, Belgium
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.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1-5 and Table 2.
Article and author information
Author details
Mélanie Boeckstaens
Gaëtan Dias Mirandela
Funding
Tenovus (S17-07)
- Arnaud Javelle
Scottish Universities Physics Alliance (NA)
- Ulrich Zachariae
Natural Environment Research Council (NE/M001415/1)
- Paul A Hoskisson
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Williamson et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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A two-lane mechanism for selective biological ammonium transport
eLife 9:e57183.
https://doi.org/10.7554/eLife.57183
