PT - JOURNAL ARTICLE AU - Gordon Williamson AU - Giulia Tamburrino AU - Gaëtan Dias Mirandela AU - Mélanie Boeckstaens AU - Marcus Bage AU - Andrei Pisliakov AU - Callum M. Ives AU - Eilidh Terras AU - Adriana Bizior AU - Paul A. Hoskisson AU - Anna Maria Marini AU - Ulrich Zachariae AU - Arnaud Javelle TI - A two-lane mechanism for selective biological ammonium transport AID - 10.1101/849562 DP - 2019 Jan 01 TA - bioRxiv PG - 849562 4099 - http://biorxiv.org/content/early/2019/11/20/849562.short 4100 - http://biorxiv.org/content/early/2019/11/20/849562.full AB - 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. A particular controversy has existed around the mechanism of ammonium exchange by the ubiquitous Amt/Mep/Rh transporter family, an essential process in all kingdoms of life. 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 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.