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[[Image:1gqt.gif|left|200px]]<br />
<applet load="1gqt" size="450" color="white" frame="true" align="right" spinBox="true"
caption="1gqt, resolution 2.34&Aring;" />
'''ACTIVATION OF RIBOKINASE BY MONOVALENT CATIONS'''<br />


==Overview==
==Activation of Ribokinase by Monovalent Cations==
Carbohydrate kinases frequently require a monovalent cation for their, activity. The physical basis of this phenomenon is, however, usually, unclear. We report here that Escherichia coli ribokinase is activated by, potassium with an apparent K(d) of 5 mM; the enzyme should therefore be, fully activated under physiological conditions. Cesium can be used as an, alternative ion, with an apparent K(d) of 17 mM. An X-ray structure of, ribokinase in the presence of cesium was solved and refined at 2.34 A, resolution. The cesium ion was bound between two loops immediately, adjacent to the anion hole of the active site. The buried location of the, site suggests that conformational changes will accompany ion binding, thus, providing a direct mechanism for activation. Comparison with structures of, a related enzyme, the adenosine kinase of Toxoplasma gondii, support this, proposal. This is apparently the first instance in which conformational, activation of a carbohydrate kinase by a monovalent cation has been, assigned a clear structural basis. The mechanism is probably general to, ribokinases, to some adenosine kinases, and to other members of the larger, family. A careful re-evaluation of the biochemical and structural data is, suggested for other enzyme systems.
<StructureSection load='1gqt' size='340' side='right'caption='[[1gqt]], [[Resolution|resolution]] 2.34&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1gqt]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli_K-12 Escherichia coli K-12]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1GQT OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1GQT 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]] 2.34&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACP:PHOSPHOMETHYLPHOSPHONIC+ACID+ADENYLATE+ESTER'>ACP</scene>, <scene name='pdbligand=CS:CESIUM+ION'>CS</scene>, <scene name='pdbligand=RIB:RIBOSE'>RIB</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=1gqt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1gqt OCA], [https://pdbe.org/1gqt PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1gqt RCSB], [https://www.ebi.ac.uk/pdbsum/1gqt PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1gqt ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/RBSK_ECOLI RBSK_ECOLI]
== 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/gq/1gqt_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=1gqt ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Carbohydrate kinases frequently require a monovalent cation for their activity. The physical basis of this phenomenon is, however, usually unclear. We report here that Escherichia coli ribokinase is activated by potassium with an apparent K(d) of 5 mM; the enzyme should therefore be fully activated under physiological conditions. Cesium can be used as an alternative ion, with an apparent K(d) of 17 mM. An X-ray structure of ribokinase in the presence of cesium was solved and refined at 2.34 A resolution. The cesium ion was bound between two loops immediately adjacent to the anion hole of the active site. The buried location of the site suggests that conformational changes will accompany ion binding, thus providing a direct mechanism for activation. Comparison with structures of a related enzyme, the adenosine kinase of Toxoplasma gondii, support this proposal. This is apparently the first instance in which conformational activation of a carbohydrate kinase by a monovalent cation has been assigned a clear structural basis. The mechanism is probably general to ribokinases, to some adenosine kinases, and to other members of the larger family. A careful re-evaluation of the biochemical and structural data is suggested for other enzyme systems.


==About this Structure==
Activation of ribokinase by monovalent cations.,Andersson CE, Mowbray SL J Mol Biol. 2002 Jan 18;315(3):409-19. PMID:11786021<ref>PMID:11786021</ref>
1GQT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with RIB, CS and ACP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Ribokinase Ribokinase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.1.15 2.7.1.15] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1GQT OCA].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
Activation of ribokinase by monovalent cations., Andersson CE, Mowbray SL, J Mol Biol. 2002 Jan 18;315(3):409-19. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11786021 11786021]
</div>
[[Category: Escherichia coli]]
<div class="pdbe-citations 1gqt" style="background-color:#fffaf0;"></div>
[[Category: Ribokinase]]
[[Category: Single protein]]
[[Category: Andersson, C.E.]]
[[Category: Mowbray, S.L.]]
[[Category: ACP]]
[[Category: CS]]
[[Category: RIB]]
[[Category: activation by monovalent cations]]
[[Category: binding of monovalent cations]]
[[Category: carbohydrate kinase]]
[[Category: induced fit]]
[[Category: ribose]]
[[Category: transferase]]


''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov  5 15:32:31 2007''
==See Also==
*[[Ribokinase 3D structures|Ribokinase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli K-12]]
[[Category: Large Structures]]
[[Category: Andersson CE]]
[[Category: Mowbray SL]]

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