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1xlk

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(New page: 200px<br /><applet load="1xlk" size="450" color="white" frame="true" align="right" spinBox="true" caption="1xlk, resolution 2.5&Aring;" /> '''MECHANISM FOR ALDOSE-...)
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[[Image:1xlk.jpg|left|200px]]<br /><applet load="1xlk" size="450" color="white" frame="true" align="right" spinBox="true"
 
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caption="1xlk, resolution 2.5&Aring;" />
 
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'''MECHANISM FOR ALDOSE-KETOSE INTERCONVERSION BY D-XYLOSE ISOMERASE INVOLVING RING OPENING FOLLOWED BY A 1,2-HYDRIDE SHIFT'''<br />
 
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==Overview==
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==MECHANISM FOR ALDOSE-KETOSE INTERCONVERSION BY D-XYLOSE ISOMERASE INVOLVING RING OPENING FOLLOWED BY A 1,2-HYDRIDE SHIFT==
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The active site and mechanism of D-xylose isomerase have been probed by, determination of the crystal structures of the enzyme bound to various, substrates, inhibitors and cations. Ring-opening is an obligatory first, step of the reaction and is believed to be the rate-determining step for, the aldose to ketose conversion. The structure of a complex with a cyclic, thio-glucose has been determined and it is concluded that this is an, analogue of the Michaelis complex. At -10 degrees C substrates in crystals, are observed in the extended chain form. The absence of an appropriately, situated base for either the cyclic or extended chain forms from the, substrate binding site indicates that the isomerisation does not take, place by an enediol or enediolate mechanism. Binding of a trivalent cation, places an additional charge at the active site, producing a substrate, complex that is analogous to a possible transition state. Of the two, binding sites for divalent cations, [1] is permanently occupied under, catalytic conditions and is co-ordinated to four carboxylate groups. In, the absence of substrate it is exposed to solvent, and in the Michaelis, complex analogue, site [1] is octahedrally coordinated, with ligands to, O-3 and O-4 of the thiopyranose. In the complex with an open-chain, substrate it remains octahedrally co-ordinated, with ligands to O-2 and, O-4. Binding at a second cation site [2] is also necessary for catalysis, and this site is believed to bind Co2+ more strongly than site [1]. This, site is octahedrally co-ordinated to three carboxylate groups (bidentate, co-ordination to one of them), an imidazole and a solvent molecule. It is, proposed that during the hydride shift the C-O-1 and C-O-2 bonds of the, substrate are polarized by the close approach of the site [2] cation. In, the transition-state analogue this cation is observed at a site [2'], 1.0, A from site [2] and about 2.7 A from O-1 and O-2 of the substrate. It is, likely that co-ordination of the cation to O-1 and O-2 would be, concomitant with ionisation of the sugar hydroxyl group. The polarisation, of C-O-1 and C-O-2 is assisted by the co-ordination of O-2 to cation [1], and O-1 to a lysine side-chain.(ABSTRACT TRUNCATED AT 400 WORDS)
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<StructureSection load='1xlk' size='340' side='right'caption='[[1xlk]], [[Resolution|resolution]] 2.50&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1xlk]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Arthrobacter_sp._NRRL_B3728 Arthrobacter sp. NRRL B3728]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XLK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1XLK FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.5&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MN:MANGANESE+(II)+ION'>MN</scene></td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1xlk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1xlk OCA], [https://pdbe.org/1xlk PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1xlk RCSB], [https://www.ebi.ac.uk/pdbsum/1xlk PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1xlk ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/XYLA_ARTS7 XYLA_ARTS7]
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/xl/1xlk_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</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=1xlk ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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1XLK is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Arthrobacter_sp. Arthrobacter sp.] with MN as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Xylose_isomerase Xylose isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.5 5.3.1.5] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1XLK OCA].
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*[[D-xylose isomerase 3D structures|D-xylose isomerase 3D structures]]
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__TOC__
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==Reference==
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</StructureSection>
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Mechanism for aldose-ketose interconversion by D-xylose isomerase involving ring opening followed by a 1,2-hydride shift., Collyer CA, Henrick K, Blow DM, J Mol Biol. 1990 Mar 5;212(1):211-35. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=2319597 2319597]
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[[Category: Arthrobacter sp. NRRL B3728]]
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[[Category: Arthrobacter sp.]]
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[[Category: Large Structures]]
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[[Category: Single protein]]
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[[Category: Blow DM]]
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[[Category: Xylose isomerase]]
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[[Category: Collyer CA]]
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[[Category: Blow, D.M.]]
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[[Category: Henrick K]]
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[[Category: Collyer, C.A.]]
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[[Category: Henrick, K.]]
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[[Category: MN]]
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[[Category: isomerase(intramolecular oxidoreductse)]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 06:09:24 2007''
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Current revision

MECHANISM FOR ALDOSE-KETOSE INTERCONVERSION BY D-XYLOSE ISOMERASE INVOLVING RING OPENING FOLLOWED BY A 1,2-HYDRIDE SHIFT

PDB ID 1xlk

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