1XQF

The mechanism of ammonia transport based on the crystal structure of AmtB of E. coli.


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.8 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.181 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

The mechanism of ammonia transport based on the crystal structure of AmtB of Escherichia coli

Zheng, L.Kostrewa, D.Berneche, S.Winkler, F.K.Li, X.-D.

(2004) Proc.Natl.Acad.Sci.USA 101: 17090-17095

  • DOI: 10.1073/pnas.0406475101
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Ammonium is one of the most important nitrogen sources for bacteria, fungi, and plants, but it is toxic to animals. The ammonium transport proteins (methylamine permeases/ammonium transporters/rhesus) are present in all domains of life; however, func ...

    Ammonium is one of the most important nitrogen sources for bacteria, fungi, and plants, but it is toxic to animals. The ammonium transport proteins (methylamine permeases/ammonium transporters/rhesus) are present in all domains of life; however, functional studies with members of this family have yielded controversial results with respect to the chemical identity (NH(4)(+) or NH(3)) of the transported species. We have solved the structure of wild-type AmtB from Escherichia coli in two crystal forms at 1.8- and 2.1-A resolution, respectively. Substrate transport occurs through a narrow mainly hydrophobic pore located at the center of each monomer of the trimeric AmtB. At the periplasmic entry, a binding site for NH(4)(+) is observed. Two phenylalanine side chains (F107 and F215) block access into the pore from the periplasmic side. Further into the pore, the side chains of two highly conserved histidine residues (H168 and H318) bridged by a H-bond lie adjacent, with their edges pointing into the cavity. These histidine residues may facilitate the deprotonation of an ammonium ion entering the pore. Adiabatic free energy calculations support the hypothesis that an electrostatic barrier between H168 and H318 hinders the permeation of cations but not that of the uncharged NH(3.) The structural data and energetic considerations strongly indicate that the methylamine permeases/ammonium transporters/rhesus proteins are ammonia gas channels. Interestingly, at the cytoplasmic exit of the pore, two different conformational states are observed that might be related to the inactivation mechanism by its regulatory partner.


    Organizational Affiliation

    Biomolecular Research, Paul Scherrer Institut, CH-5232, Villigen, Switzerland.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Probable ammonium transporter
A
418Escherichia coli (strain K12)Mutation(s): 0 
Gene Names: amtB (ybaG)
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
Channels: Amt/Mep/Rh proteins
Protein: 
AmtB ammonia channel (mutant)
Find proteins for P69681 (Escherichia coli (strain K12))
Go to UniProtKB:  P69681
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
ACT
Query on ACT

Download SDF File 
Download CCD File 
A
ACETATE ION
C2 H3 O2
QTBSBXVTEAMEQO-UHFFFAOYSA-M
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.8 Å
  • R-Value Free: 0.208 
  • R-Value Work: 0.181 
  • Space Group: P 63
Unit Cell:
Length (Å)Angle (°)
a = 111.800α = 90.00
b = 111.800β = 90.00
c = 86.400γ = 120.00
Software Package:
Software NamePurpose
MAR345data collection
XDSdata scaling
REFMACrefinement
SHARPphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2004-10-26
    Type: Initial release
  • Version 1.1: 2008-04-30
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance
  • Version 1.3: 2017-10-11
    Type: Refinement description