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Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB
- A. Javelle, D. Lupo, P. Ripoche, Tim Fulford, M. Merrick, F. Winkler
- BiologyProceedings of the National Academy of Sciences
- 1 April 2008
It is concluded that substrate deprotonation is an essential part of the conduction mechanism, but the possibility of net electrogenic transport is not ruled out.
The conserved carboxy-terminal region of the ammonia channel AmtB plays a critical role in channel function
Using the Escherichia coli AmtB protein as a model system for Amt proteins, an extensive site-directed mutagenesis study indicates that nearly all mutations fall into two phenotypic classes that are best explained in terms of two distinct effects of the C-terminal region on AmTB activity.
Ammonium Sensing in Escherichia coli
It is shown that Escherichia coli AmtB is inactivated by formation of a membrane-bound complex with GlnK, which provides an exquisitely sensitive mechanism to control ammonium flux into the cell, and the conservation of glnK linkage to amtB suggests that this regulatory mechanism may occur throughout prokaryotes.
In vivo functional characterization of the Escherichia coli ammonium channel AmtB: evidence for metabolic coupling of AmtB to glutamine synthetase.
- A. Javelle, G. Thomas, A. Marini, R. Krämer, M. Merrick
- Biology, ChemistryThe Biochemical journal
- 15 August 2005
The role that AmtB plays in ammonium/methylammonium transport is examined, in the light of conflicting proposals with regard to both the mode of action of Amt proteins and their substrate, i.e. ammonia or ammonium.
An update on nutrient transport processes in ectomycorrhizas
Nutrient transport, namely absorption from the soil solution as well as nutrient transfer from fungus to plant and carbon movement from plant to fungus are key features of mycorrhizal symbiosis. This…
An Unusual Twin-His Arrangement in the Pore of Ammonia Channels Is Essential for Substrate Conductance*
- A. Javelle, D. Lupo, Lei Zheng, Xiao-dan Li, F. Winkler, M. Merrick
- BiologyJournal of Biological Chemistry
- 22 December 2006
It is shown that both histidines are absolutely required for optimum substrate conductance in Escherichia coli AmtB and in a subgroup of Amt proteins, found only in fungi, one of the histidine residues is replaced by glutamate.
Molecular characterization, function and regulation of ammonium transporters (Amt) and ammonium‐metabolizing enzymes (GS, NADP‐GDH) in the ectomycorrhizal fungus Hebeloma cylindrosporum
Cloned and characterized Hebeloma cylindrosporum AMT1, GLNA and GDHA genes, which encode a third ammonium transporter, a glutamine synthetase and an NADP‐dependent glutamate dehydrogenase respectively, and identified the intracellular nitrogen pool(s) responsible for the modulation of expression of AMT2, AMT3, GDHA and GLNA.
Transport mechanisms in the ammonium transporter family.
The Escherichia coli SLC26 homologue YchM (DauA) is a C4‐dicarboxylic acid transporter
This is the first report that a SLC26/SulP protein acts as a C4‐dicarboxylic acid transporter and an unexpected new function for a prokaryotic member of this transporter family is reported.