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| [[Image:1x28.gif|left|200px]]<br /><applet load="1x28" size="450" color="white" frame="true" align="right" spinBox="true"
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| caption="1x28, resolution 2.40Å" />
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| '''Crystal Structure of e.coli AspAT complexed with N-phosphopyridoxyl-L-glutamic acid'''<br />
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| ==Overview== | | ==Crystal Structure of e.coli AspAT complexed with N-phosphopyridoxyl-L-glutamic acid== |
| The mechanism for the reaction of aspartate aminotransferase with the C4, substrate, l-aspartate, has been well established. The binding of the C4, substrate induces conformational change in the enzyme from the open to the, closed form, and the entire reaction proceeds in the closed form of the, enzyme. On the contrary, little is known about the reaction with the C5, substrate, l-glutamate. In this study, we analyzed the pH-dependent, binding of 2-methyl-l-glutamate to the enzyme and showed that the, interaction between the amino group of 2-methyl-l-glutamate and the, pyridoxal 5'-phosphate aldimine is weak compared to that between, 2-methyl-l-aspartate and the aldimine. The structures of the Michaelis, complexes of the enzyme with l-aspartate and l-glutamate were modeled on, the basis of the maleate and glutarate complex structures of the enzyme., The result showed that l-glutamate binds to the open form of the enzyme in, an extended conformation, and its alpha-amino group points in the opposite, direction of the aldimine, while that of l-aspartate is close to the, aldimine. These models explain the observations for 2-methyl-l-glutamate, and 2-methyl-l-aspartate. The crystal structures of the complexes of, aspartate aminotransferase with phosphopyridoxyl derivatives of, l-glutamate, d-glutamate, and 2-methyl-l-glutamate were solved as the, models for the external aldimine and ketimine complexes of l-glutamate., All the structures were in the closed form, and the two carboxylate groups, and the arginine residues binding them are superimposable on the external, aldimine complex with 2-methyl-l-aspartate. Taking these facts altogether, it was strongly suggested that the binding of l-glutamate to aspartate, aminotransferase to form the Michaelis complex does not induce a, conformational change in the enzyme, and that the conformational change to, the closed form occurs during the transaldimination step. The hydrophobic, residues of the entrance of the active site, including Tyr70, are, considered to be important for promoting the transaldimination process and, hence the recognition of the C5 substrate.
| | <StructureSection load='1x28' size='340' side='right'caption='[[1x28]], [[Resolution|resolution]] 2.40Å' scene=''> |
| | == Structural highlights == |
| | <table><tr><td colspan='2'>[[1x28]] 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=1X28 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1X28 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]] 2.4Å</td></tr> |
| | <tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=PGU:N-({3-HYDROXY-2-METHYL-5-[(PHOSPHONOOXY)METHYL]PYRIDIN-4-YL}METHYL)-L-GLUTAMIC+ACID'>PGU</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=1x28 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1x28 OCA], [https://pdbe.org/1x28 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1x28 RCSB], [https://www.ebi.ac.uk/pdbsum/1x28 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1x28 ProSAT]</span></td></tr> |
| | </table> |
| | == Function == |
| | [https://www.uniprot.org/uniprot/AAT_ECOLI AAT_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/x2/1x28_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=1x28 ConSurf]. |
| | <div style="clear:both"></div> |
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| ==About this Structure== | | ==See Also== |
| 1X28 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 PGU as [http://en.wikipedia.org/wiki/ligand ligand]. 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=1X28 OCA].
| | *[[Aspartate aminotransferase 3D structures|Aspartate aminotransferase 3D structures]] |
| | | __TOC__ |
| ==Reference==
| | </StructureSection> |
| Binding of C5-dicarboxylic substrate to aspartate aminotransferase: implications for the conformational change at the transaldimination step., Islam MM, Goto M, Miyahara I, Ikushiro H, Hirotsu K, Hayashi H, Biochemistry. 2005 Jun 14;44(23):8218-29. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=15938611 15938611]
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| [[Category: Aspartate transaminase]]
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| [[Category: Escherichia coli]] | | [[Category: Escherichia coli]] |
| [[Category: Single protein]] | | [[Category: Large Structures]] |
| [[Category: Goto, M.]] | | [[Category: Goto M]] |
| [[Category: PGU]]
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| [[Category: plp-dependent enzyme]]
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| ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 05:48:13 2007''
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