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1aic

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(New page: 200px<br /><applet load="1aic" size="450" color="white" frame="true" align="right" spinBox="true" caption="1aic, resolution 2.40&Aring;" /> '''STRUCTURAL BASIS FOR...)
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[[Image:1aic.jpg|left|200px]]<br /><applet load="1aic" size="450" color="white" frame="true" align="right" spinBox="true"
 
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caption="1aic, resolution 2.40&Aring;" />
 
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'''STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING THE PYRIDOXAL-5'-PHSOPHATE BINDING LYSINE RESIDUE'''<br />
 
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==Overview==
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==STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING THE PYRIDOXAL-5'-PHOSPHATE BINDING LYSINE RESIDUE==
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Chicken mitochondrial and Escherichia coli aspartate aminotransferases, K258H, in which the active site lysine residue has been exchanged for a, histidine residue, retain partial catalytic competence [Ziak et al. (1993), Eur. J. Biochem. 211, 475-484]. Mutant PLP and PMP holoenzymes and the, complexes of the latter (E. coli enzyme) with sulfate and 2-oxoglutarate, as well as complexes of the mitochondrial apoenzyme with, N-(5'-phosphopyridoxyl)-L-aspartate or, N-(5'-phosphopyridoxyl)-L-glutamate, were crystallized and analyzed by, means of X-ray crystallography in order to examine how the side chain of, histidine 258 can substitute as a general acid/base catalyst of the, aldimine-ketimine tautomerization in enzymic transamination. The, structures have been solved and refined at resolutions between 2.1 and 2.8, A. Both the closed and the open conformations, identical to those of the, wild-type enzyme, were observed, indicating that the mutant enzymes of, both species exhibit the same conformational flexibility as the wild-type, enzymes, although in AspAT K258H the equilibrium is somewhat shifted, toward the open conformation. The replacement of the active site K258 by a, histidine residue resulted only in local structural adaptations necessary, to accommodate the imidazole ring. The catalytic competence of the mutant, enzyme, which in the forward half-reaction is 0.1% of that of the, wild-type enzyme, suggests that the imidazole group is involved in the, aldimine-ketimine tautomerization. However, the imidazole ring of H258 is, too far away from C alpha and C4' of the coenzyme-substrate adduct for, direct proton transfer, suggesting that the 1,3-prototropic shift is, mediated by a water molecule. Although there is enough space for a water, molecule in this area, it has not been detected. Dynamic fluctuations of, the protein matrix might transiently open a channel, giving a water, molecule fleeting access to the active site.
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<StructureSection load='1aic' size='340' side='right'caption='[[1aic]], [[Resolution|resolution]] 2.40&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1aic]] is a 2 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=1AIC OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1AIC 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]] 2.4&#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=PMP:4-DEOXY-4-AMINOPYRIDOXAL-5-PHOSPHATE'>PMP</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=1aic FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1aic OCA], [https://pdbe.org/1aic PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1aic RCSB], [https://www.ebi.ac.uk/pdbsum/1aic PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1aic ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/AAT_ECOLI AAT_ECOLI]
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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/ai/1aic_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=1aic 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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1AIC 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 SO4 and PMP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AIC OCA].
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*[[Aspartate aminotransferase 3D structures|Aspartate aminotransferase 3D structures]]
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__TOC__
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==Reference==
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</StructureSection>
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Structural basis for the catalytic activity of aspartate aminotransferase K258H lacking the pyridoxal 5'-phosphate-binding lysine residue., Malashkevich VN, Jager J, Ziak M, Sauder U, Gehring H, Christen P, Jansonius JN, Biochemistry. 1995 Jan 17;34(2):405-14. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=7819232 7819232]
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[[Category: Aspartate transaminase]]
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[[Category: Escherichia coli]]
[[Category: Escherichia coli]]
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[[Category: Single protein]]
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[[Category: Large Structures]]
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[[Category: Jaeger, J.]]
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[[Category: Jaeger J]]
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[[Category: Jansonius, J.N.]]
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[[Category: Jansonius JN]]
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[[Category: PMP]]
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[[Category: SO4]]
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[[Category: transferase(aminotransferase)]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 10:52:48 2007''
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Current revision

STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING THE PYRIDOXAL-5'-PHOSPHATE BINDING LYSINE RESIDUE

PDB ID 1aic

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