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1aib

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[[Image:1aib.gif|left|200px]]<br /><applet load="1aib" size="350" color="white" frame="true" align="right" spinBox="true"
 
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caption="1aib, resolution 2.80&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='1aib' size='340' side='right'caption='[[1aib]], [[Resolution|resolution]] 2.80&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1aib]] 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=1AIB OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1AIB 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]] 2.8&#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=AKG:2-OXOGLUTARIC+ACID'>AKG</scene>, <scene name='pdbligand=PMP:4-DEOXY-4-AMINOPYRIDOXAL-5-PHOSPHATE'>PMP</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=1aib FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1aib OCA], [https://pdbe.org/1aib PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1aib RCSB], [https://www.ebi.ac.uk/pdbsum/1aib PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1aib 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/1aib_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=1aib 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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1AIB 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 <scene name='pdbligand=PMP:'>PMP</scene> and <scene name='pdbligand=AKG:'>AKG</scene> 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://oca.weizmann.ac.il/oca-bin/ocashort?id=1AIB 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: AKG]]
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[[Category: PMP]]
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[[Category: transferase(aminotransferase)]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:44:49 2008''
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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 1aib

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