Mécanismes de transport dans le pore des transporteurs d’ammonium

G Lamoureux, A Javelle, S Baday, S Wang, S Bernèche

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data.

Translated title of the contributionMécanismes de transport dans le pore des transporteurs d’ammonium
LanguageMultiple languages
Pages168-175
Number of pages8
JournalTransfusion clinique et biologique : journal de la Société française de transfusion sanguine
Volume17
Issue number3
DOIs
Publication statusPublished - 1 Sep 2010

Fingerprint

Ammonium Compounds
Molecules
X-Rays
Permeation
X rays
Proteins
Molecular mechanics
Water
X ray crystallography
X Ray Crystallography
Ion Transport
Mechanics
Ammonia
Escherichia coli
Membrane Proteins
Salts
Availability
Crystals
Experiments

Keywords

  • amino acid sequence
  • ammonia
  • animals
  • binding sites
  • biological transport
  • cation transport proteins
  • conserved sequence
  • crystallography, X-ray
  • Escherichia coli proteins
  • ion transport
  • models, biological
  • models, molecular
  • quaternary ammonium compounds

Cite this

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title = "Transport mechanisms in the ammonium transporter family",
abstract = "Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data.",
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author = "G Lamoureux and A Javelle and S Baday and S Wang and S Bern{\`e}che",
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Transport mechanisms in the ammonium transporter family. / Lamoureux, G; Javelle, A; Baday, S; Wang, S; Bernèche, S.

In: Transfusion clinique et biologique : journal de la Société française de transfusion sanguine, Vol. 17, No. 3, 01.09.2010, p. 168-175.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Transport mechanisms in the ammonium transporter family

AU - Lamoureux, G

AU - Javelle, A

AU - Baday, S

AU - Wang, S

AU - Bernèche, S

N1 - Copyright 2010 Elsevier Masson SAS. All rights reserved.

PY - 2010/9/1

Y1 - 2010/9/1

N2 - Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data.

AB - Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data.

KW - amino acid sequence

KW - ammonia

KW - animals

KW - binding sites

KW - biological transport

KW - cation transport proteins

KW - conserved sequence

KW - crystallography, X-ray

KW - Escherichia coli proteins

KW - ion transport

KW - models, biological

KW - models, molecular

KW - quaternary ammonium compounds

U2 - 10.1016/j.tracli.2010.06.004

DO - 10.1016/j.tracli.2010.06.004

M3 - Article

VL - 17

SP - 168

EP - 175

JO - Transfusion clinique et biologique : journal de la Société française de transfusion sanguine

T2 - Transfusion clinique et biologique : journal de la Société française de transfusion sanguine

JF - Transfusion clinique et biologique : journal de la Société française de transfusion sanguine

SN - 1246-7820

IS - 3

ER -