A two-lane mechanism for selective biological ammonium transport

Williamson, Gordon and Tamburrino, Guila and Bizior, Adriana and Boeckstaens, Mélanie and Dias Mirandela, Gaëtan and Bage, Marcus G and Pisliakov, Andrei and Ives, Callum M and Terras, Eilidh and Hoskisson, Paul A and Marini, Anna Maria and Zachariae, Ulrich and Javelle, Arnaud (2020) A two-lane mechanism for selective biological ammonium transport. eLife, 9. e57183. ISSN 2050-084X

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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.

    ORCID iDs

    Williamson, Gordon, Tamburrino, Guila, Bizior, Adriana, Boeckstaens, Mélanie, Dias Mirandela, Gaëtan ORCID logoORCID: https://orcid.org/0000-0001-5871-6288, Bage, Marcus G, Pisliakov, Andrei, Ives, Callum M, Terras, Eilidh, Hoskisson, Paul A ORCID logoORCID: https://orcid.org/0000-0003-4332-1640, Marini, Anna Maria, Zachariae, Ulrich and Javelle, Arnaud ORCID logoORCID: https://orcid.org/0000-0002-3611-5737;