Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
J Biol Chem
2020 Mar 06;29510:3362-3370. doi: 10.1074/jbc.RA119.010891.
Show Gene links
Show Anatomy links
A twin histidine motif is the core structure for high-affinity substrate selection in plant ammonium transporters.
Ganz P
,
Ijato T
,
Porras-Murrilo R
,
Stührwohldt N
,
Ludewig U
,
Neuhäuser B
.
???displayArticle.abstract???
Ammonium transporters (AMT), methylamine permeases (Mep), and the more distantly related rhesus factors (Rh) are trimeric membrane proteins present in all domains of life. AMT/Mep/Rhs are highly selective membrane proteins required for ammonium uptake or release, and they efficiently exclude the similarly sized K+ ion. Previously reported crystal structures have revealed that each transporter subunit contains a unique hydrophobic but occluded central pore, but it is unclear whether the base (NH3) or NH3 coupled with an H+ are transported. Here, using expression of two plant AMTs (AtAMT1;2 and AMT2) in budding yeast, we found that systematic replacements in the conserved twin-histidine motif, a hallmark of most AMT/Mep/Rh, alter substrate recognition, transport capacities, N isotope selection, and selectivity against K+ AMT-specific differences were found for histidine variants. Variants that completely lost ammonium N isotope selection, a feature likely associated with NH4+ deprotonation during passage, substantially transported K+ in addition to NH4+ Of note, the twin-histidine motif was not essential for ammonium transport. However, it conferred key AMT features, such as high substrate affinity and selectivity against alkali cations via an NH4+ deprotonation mechanism. Our findings indicate that the twin-His motif is the core structure responsible for substrate deprotonation and isotopic preferences in AMT pores and that decreased deprotonation capacity is associated with reduced selectivity against K+ We conclude that optimization for ammonium transport in plant AMT represents a compromise between substrate deprotonation for optimal selectivity and high substrate affinity and transport rates.
Andrade,
Crystal structure of the archaeal ammonium transporter Amt-1 from Archaeoglobus fulgidus.
2005, Pubmed
Andrade,
Crystal structure of the archaeal ammonium transporter Amt-1 from Archaeoglobus fulgidus.
2005,
Pubmed
Ariz,
Nitrogen isotope signature evidences ammonium deprotonation as a common transport mechanism for the AMT-Mep-Rh protein superfamily.
2018,
Pubmed
Biver,
A role for Rhesus factor Rhcg in renal ammonium excretion and male fertility.
2008,
Pubmed
Boogerd,
AmtB-mediated NH3 transport in prokaryotes must be active and as a consequence regulation of transport by GlnK is mandatory to limit futile cycling of NH4(+)/NH3.
2011,
Pubmed
Doyle,
The structure of the potassium channel: molecular basis of K+ conduction and selectivity.
1998,
Pubmed
Fong,
The W148L substitution in the Escherichia coli ammonium channel AmtB increases flux and indicates that the substrate is an ion.
2007,
Pubmed
Ganz,
A pore-occluding phenylalanine gate prevents ion slippage through plant ammonium transporters.
2019,
Pubmed
Hall,
The pivotal twin histidines and aromatic triad of the Escherichia coli ammonium channel AmtB can be replaced.
2011,
Pubmed
Hall,
The molecular basis of K+ exclusion by the Escherichia coli ammonium channel AmtB.
2013,
Pubmed
Haro,
Cloning of two genes encoding potassium transporters in Neurospora crassa and expression of the corresponding cDNAs in Saccharomyces cerevisiae.
1999,
Pubmed
Hirsch,
A role for the AKT1 potassium channel in plant nutrition.
1998,
Pubmed
Javelle,
An unusual twin-his arrangement in the pore of ammonia channels is essential for substrate conductance.
2006,
Pubmed
Khademi,
Mechanism of ammonia transport by Amt/MEP/Rh: structure of AmtB at 1.35 A.
2004,
Pubmed
Kleiner,
The transport of NH3 and NH4+ across biological membranes.
1981,
Pubmed
Ludewig,
Electroneutral ammonium transport by basolateral rhesus B glycoprotein.
2004,
Pubmed
,
Xenbase
Ludewig,
Molecular mechanisms of ammonium transport and accumulation in plants.
2007,
Pubmed
Ludewig,
Uniport of NH4+ by the root hair plasma membrane ammonium transporter LeAMT1;1.
2002,
Pubmed
,
Xenbase
Lupo,
The 1.3-A resolution structure of Nitrosomonas europaea Rh50 and mechanistic implications for NH3 transport by Rhesus family proteins.
2007,
Pubmed
Luzhkov,
Computational study of the binding affinity and selectivity of the bacterial ammonium transporter AmtB.
2006,
Pubmed
Marini,
A family of ammonium transporters in Saccharomyces cerevisiae.
1997,
Pubmed
Mayer,
Different transport mechanisms in plant and human AMT/Rh-type ammonium transporters.
2006,
Pubmed
,
Xenbase
Mayer,
Ammonium ion transport by the AMT/Rh homologue LeAMT1;1.
2006,
Pubmed
,
Xenbase
Mirandela,
The lipid environment determines the activity of the Escherichia coli ammonium transporter AmtB.
2019,
Pubmed
Musa-Aziz,
Relative CO2/NH3 selectivities of AQP1, AQP4, AQP5, AmtB, and RhAG.
2009,
Pubmed
,
Xenbase
Neuhäuser,
Regulation of NH4+ transport by essential cross talk between AMT monomers through the carboxyl tails.
2007,
Pubmed
Neuhäuser,
Switching substrate specificity of AMT/MEP/ Rh proteins.
2014,
Pubmed
Neuhäuser,
Channel-like NH3 flux by ammonium transporter AtAMT2.
2009,
Pubmed
,
Xenbase
Nygaard,
Ammonium recruitment and ammonia transport by E. coli ammonia channel AmtB.
2006,
Pubmed
Pardo,
Extracellular K+ specifically modulates a rat brain K+ channel.
1992,
Pubmed
,
Xenbase
Ripoche,
Human Rhesus-associated glycoprotein mediates facilitated transport of NH(3) into red blood cells.
2004,
Pubmed
Rodriguez-Navarro,
A potassium-proton symport in Neurospora crassa.
1986,
Pubmed
Sohlenkamp,
Characterization of Arabidopsis AtAMT2, a high-affinity ammonium transporter of the plasma membrane.
2002,
Pubmed
van den Berg,
Structural basis for Mep2 ammonium transceptor activation by phosphorylation.
2016,
Pubmed
Wang,
Ammonium Uptake by Rice Roots (III. Electrophysiology).
1994,
Pubmed
Yuan,
The organization of high-affinity ammonium uptake in Arabidopsis roots depends on the spatial arrangement and biochemical properties of AMT1-type transporters.
2007,
Pubmed
Zheng,
The mechanism of ammonia transport based on the crystal structure of AmtB of Escherichia coli.
2004,
Pubmed
