Lipid-associated architecture and divergent ammonium transport distinguish a bacterial Rhesus protein
- 1University of Oxford
Abstract
Nitrification is a major process in the global nitrogen cycle, initiated by the oxidation of ammonia to nitrite. The ammonia-oxidising bacterium Nitrosomonas europaea catalyses this first and rate-limiting step and depends on ammonium both as an energy substrate and as a nitrogen source, making ammonium acquisition central to its physiology. Cellular ammonium transport is mediated by the Amt/Mep/Rh superfamily, whose members share a conserved fold despite divergent physiological roles. Remarkably, N. europaea lacks a canonical prokaryotic Amt transporter and instead expresses NeRh50, a Rh-family protein proposed to have been acquired from a eukaryotic lineage. Here, we determine a cryo-EM structure of NeRh50 that reveals tightly associated lipids at the monomer-monomer interfaces, including density consistent with an unusual inverted lipid orientation. Native mass spectrometry and molecular dynamics simulations further support persistent lipid association at these interfaces. NeRh50 also differs functionally from canonical AmtB, selectively mediating electrogenic ammonium transport with ~70-fold lower apparent affinity. Transport is enhanced under alkaline conditions but not by an imposed proton gradient, suggesting membrane-potential dependence. Together, these findings reveal divergence from canonical Amt proteins in both membrane-associated architecture and transport properties, providing insight into the functional and evolutionary diversification of the Amt/Mep/Rh superfamily.
Related
- Interlayer Architecture Modulates Water State and Transport in Chitosan Aerogels for Solar-Driven Interfacial Evaporation
- Alignment and directional ionic transport in liquid-crystalline and related ordered soft electrolytes: a 25-study evidence map with an architecture-aware comparability audit
- Morgan Fingerprint Classification Prioritizes Autophagy Modulators While Transcriptome Regression Fails to Distinguish Opposing Modulators
- Conserved recognition and divergent peripheral dynamics of designed statin analogues at human HMG-CoA reductase: ensemble docking and replicated molecular dynamics
- Remote N‑Substituent‑Tuned Dichotomous Diradical Scission Enables Photocatalytic Divergent Rearrangement of Allylic Aminophosphines
BibTeX
@misc{cooper2026lipidassociated,
title = {{Lipid-associated architecture and divergent ammonium transport distinguish a bacterial Rhesus protein}},
author = {B. Cooper and A. Bizior and R. Talandashti and A. Oluwole and P. Henderson and T. Harris and C. Robinson and P. Hoskisson and S. Khalid and L. Pritchard and G. Isom and A. Javelle},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.17.752382},
url = {https://www.biorxiv.org/content/10.64898/2026.09.17.752382v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Lipid-associated architecture and divergent ammonium transport distinguish a bacterial Rhesus protein
AU - B. Cooper
AU - A. Bizior
AU - R. Talandashti
AU - A. Oluwole
AU - P. Henderson
AU - T. Harris
AU - C. Robinson
AU - P. Hoskisson
AU - S. Khalid
AU - L. Pritchard
AU - G. Isom
AU - A. Javelle
PY - 2026
DA - 2026/09/17
PB - bioRxiv
DO - 10.64898/2026.09.17.752382
UR - https://www.biorxiv.org/content/10.64898/2026.09.17.752382v1
AB - Nitrification is a major process in the global nitrogen cycle, initiated by the oxidation of ammonia to nitrite. The ammonia-oxidising bacterium Nitrosomonas europaea catalyses this first and rate-limiting step and depends on ammonium both as an energy substrate and as a nitrogen source, making ammonium acquisition central to its physiology. Cellular ammonium transport is mediated by the Amt/Mep/Rh superfamily, whose members share a conserved fold despite divergent physiological roles. Remarkably, N. europaea lacks a canonical prokaryotic Amt transporter and instead expresses NeRh50, a Rh-family protein proposed to have been acquired from a eukaryotic lineage. Here, we determine a cryo-EM structure of NeRh50 that reveals tightly associated lipids at the monomer-monomer interfaces, including density consistent with an unusual inverted lipid orientation. Native mass spectrometry and molecular dynamics simulations further support persistent lipid association at these interfaces. NeRh50 also differs functionally from canonical AmtB, selectively mediating electrogenic ammonium transport with ~70-fold lower apparent affinity. Transport is enhanced under alkaline conditions but not by an imposed proton gradient, suggesting membrane-potential dependence. Together, these findings reveal divergence from canonical Amt proteins in both membrane-associated architecture and transport properties, providing insight into the functional and evolutionary diversification of the Amt/Mep/Rh superfamily.
ER -