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[[Image:1g4x.jpg|left|200px]]<br /><applet load="1g4x" size="350" color="white" frame="true" align="right" spinBox="true"
caption="1g4x, resolution 2.2&Aring;" />
'''ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L'''<br />


==Overview==
==ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L==
Systematic single and multiple replacement studies have been applied to Escherichia coli aspartate aminotransferase to probe the electrostatic effect of the two substrate-binding arginine residues, Arg292 and Arg386, and the structural effect of the pyridoxal 5'-phosphate-Asn194-Arg386 hydrogen-bond linkage system (PLP-N-R) on the pK(a) value of the Schiff base formed between pyridoxal 5'-phosphate (PLP) and Lys258. The electrostatic effects of the two arginine residues cannot be assessed by simple mutational studies of the residues. PLP-N-R lowers the pK(a) value of the PLP-Lys258 Schiff base by keeping it in the distorted conformation, which is unfavorable for protonation. Mutation of Arg386 eliminates its hydrogen bond with Asn194 and partially disrupts PLP-N-R, thereby relaxing the strain of the Schiff base. On the other hand, mutation of Arg292, the large domain residue that interacts with the small domain residue Asp15, makes the domain opening easier. Because PLP-N-R lies between the two domains, the domain opening increases the strain of the Schiff base. Therefore, the true electrostatic effects of Arg292 and Arg386 could be derived from mutational analysis of the enzyme in which PLP-N-R had been completely disrupted by the Asn194Ala mutation. Through the analyses, we could dissect the electrostatic and structural effects of the arginine mutations on the Schiff base pK(a). The positive charges of the two arginine residues and the PLP-N-R-mediated strain of the Schiff base lower the Schiff base pK(a) by 0.7 and 1.7, respectively. Thus, the electrostatic effect of the arginine residues is not as strong as has historically been thought, and this finding substantiates our recent finding that the imine-pyridine torsion of the Schiff base is the primary determinant (2.8 unit decrease) of the extremely low pK(a) value of the Schiff base [Hayashi, H., Mizuguchi, H., and Kagamiyama, H. (1998) Biochemistry 37, 15076-15085].
<StructureSection load='1g4x' size='340' side='right'caption='[[1g4x]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1g4x]] is a 1 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=1G4X OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1G4X 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]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=PLP:PYRIDOXAL-5-PHOSPHATE'>PLP</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=1g4x FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1g4x OCA], [https://pdbe.org/1g4x PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1g4x RCSB], [https://www.ebi.ac.uk/pdbsum/1g4x PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1g4x 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/g4/1g4x_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=1g4x ConSurf].
<div style="clear:both"></div>


==About this Structure==
==See Also==
1G4X 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=PLP:'>PLP</scene> 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://oca.weizmann.ac.il/oca-bin/ocashort?id=1G4X OCA].
*[[Aspartate aminotransferase 3D structures|Aspartate aminotransferase 3D structures]]
 
__TOC__
==Reference==
</StructureSection>
Strain is more important than electrostatic interaction in controlling the pKa of the catalytic group in aspartate aminotransferase., Mizuguchi H, Hayashi H, Okada K, Miyahara I, Hirotsu K, Kagamiyama H, Biochemistry. 2001 Jan 16;40(2):353-60. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11148029 11148029]
[[Category: Aspartate transaminase]]
[[Category: Escherichia coli]]
[[Category: Escherichia coli]]
[[Category: Single protein]]
[[Category: Large Structures]]
[[Category: Mizuguchi, H.]]
[[Category: Mizuguchi H]]
[[Category: PLP]]
[[Category: active site mutant]]
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:46:10 2008''

Latest revision as of 14:19, 27 March 2024

ASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292LASPARTATE AMINOTRANSFERASE ACTIVE SITE MUTANT N194A/R292L

Structural highlights

1g4x is a 1 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:X-ray diffraction, Resolution 2.2Å
Ligands:
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

AAT_ECOLI

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

1g4x, resolution 2.20Å

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