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==Substrate binding, deprotonation and selectivity at the periplasmic entrance of the E. coli ammonia channel AmtB== | |||
<StructureSection load='3c1h' size='340' side='right'caption='[[3c1h]], [[Resolution|resolution]] 2.20Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[3c1h]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3C1H OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3C1H FirstGlance]. <br> | |||
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.2Å</td></tr> | |||
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=IMD:IMIDAZOLE'>IMD</scene>, <scene name='pdbligand=LDA:LAURYL+DIMETHYLAMINE-N-OXIDE'>LDA</scene></td></tr> | |||
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=3c1h FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3c1h OCA], [https://pdbe.org/3c1h PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3c1h RCSB], [https://www.ebi.ac.uk/pdbsum/3c1h PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3c1h ProSAT]</span></td></tr> | |||
</table> | |||
== Function == | |||
[https://www.uniprot.org/uniprot/AMTB_ECOLI AMTB_ECOLI] Involved in the uptake of ammonia. | |||
== Evolutionary Conservation == | |||
[[Image:Consurf_key_small.gif|200px|right]] | |||
Check<jmol> | |||
<jmolCheckbox> | |||
<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/c1/3c1h_consurf.spt"</scriptWhenChecked> | |||
<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked> | |||
<text>to colour the structure by Evolutionary Conservation</text> | |||
</jmolCheckbox> | |||
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=3c1h ConSurf]. | |||
<div style="clear:both"></div> | |||
<div style="background-color:#fffaf0;"> | |||
== Publication Abstract from PubMed == | |||
The conduction mechanism of Escherichia coli AmtB, the structurally and functionally best characterized representative of the ubiquitous Amt/Rh family, has remained controversial in several aspects. The predominant view has been that it facilitates the movement of ammonium in its uncharged form as indicated by the hydrophobic nature of a pore located in the center of each subunit of the homotrimer. Using site-directed mutagenesis and a combination of biochemical and crystallographic methods, we have investigated mechanistic questions concerning the putative periplasmic ammonium ion binding site S1 and the adjacent periplasmic "gate" formed by two highly conserved phenylalanine residues, F107 and F215. Our results challenge models that propose that NH(4)(+) deprotonation takes place at S1 before NH(3) conduction through the pore. The presence of S1 confers two critical features on AmtB, both essential for its function: ammonium scavenging efficiency at very low ammonium concentration and selectivity against water and physiologically important cations. We show that AmtB activity absolutely requires F215 but not F107 and that removal or obstruction of the phenylalanine gate produces an open but inactive channel. The phenyl ring of F215 must thus play a very specific role in promoting transfer and deprotonation of substrate from S1 to the central pore. We discuss these results with respect to three distinct mechanisms of conduction that have been considered so far. We conclude that substrate deprotonation is an essential part of the conduction mechanism, but we do not rule out net electrogenic transport. | |||
Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB.,Javelle A, Lupo D, Ripoche P, Fulford T, Merrick M, Winkler FK Proc Natl Acad Sci U S A. 2008 Apr 1;105(13):5040-5. Epub 2008 Mar 24. PMID:18362341<ref>PMID:18362341</ref> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
</div> | |||
<div class="pdbe-citations 3c1h" style="background-color:#fffaf0;"></div> | |||
== | ==See Also== | ||
*[[Ion channels 3D structures|Ion channels 3D structures]] | |||
== References == | |||
<references/> | |||
__TOC__ | |||
</StructureSection> | |||
[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: | [[Category: Large Structures]] | ||
[[Category: Lupo | [[Category: Lupo D]] | ||
[[Category: Winkler | [[Category: Winkler FK]] | ||
Latest revision as of 17:54, 1 November 2023
Substrate binding, deprotonation and selectivity at the periplasmic entrance of the E. coli ammonia channel AmtBSubstrate binding, deprotonation and selectivity at the periplasmic entrance of the E. coli ammonia channel AmtB
Structural highlights
FunctionAMTB_ECOLI Involved in the uptake of ammonia. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe conduction mechanism of Escherichia coli AmtB, the structurally and functionally best characterized representative of the ubiquitous Amt/Rh family, has remained controversial in several aspects. The predominant view has been that it facilitates the movement of ammonium in its uncharged form as indicated by the hydrophobic nature of a pore located in the center of each subunit of the homotrimer. Using site-directed mutagenesis and a combination of biochemical and crystallographic methods, we have investigated mechanistic questions concerning the putative periplasmic ammonium ion binding site S1 and the adjacent periplasmic "gate" formed by two highly conserved phenylalanine residues, F107 and F215. Our results challenge models that propose that NH(4)(+) deprotonation takes place at S1 before NH(3) conduction through the pore. The presence of S1 confers two critical features on AmtB, both essential for its function: ammonium scavenging efficiency at very low ammonium concentration and selectivity against water and physiologically important cations. We show that AmtB activity absolutely requires F215 but not F107 and that removal or obstruction of the phenylalanine gate produces an open but inactive channel. The phenyl ring of F215 must thus play a very specific role in promoting transfer and deprotonation of substrate from S1 to the central pore. We discuss these results with respect to three distinct mechanisms of conduction that have been considered so far. We conclude that substrate deprotonation is an essential part of the conduction mechanism, but we do not rule out net electrogenic transport. Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB.,Javelle A, Lupo D, Ripoche P, Fulford T, Merrick M, Winkler FK Proc Natl Acad Sci U S A. 2008 Apr 1;105(13):5040-5. Epub 2008 Mar 24. PMID:18362341[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences |
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