6nx8: Difference between revisions

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<StructureSection load='6nx8' size='340' side='right'caption='[[6nx8]], [[Resolution|resolution]] 1.85&Aring;' scene=''>
<StructureSection load='6nx8' size='340' side='right'caption='[[6nx8]], [[Resolution|resolution]] 1.85&Aring;' scene=''>
== Structural highlights ==
== Structural highlights ==
<table><tr><td colspan='2'>[[6nx8]] is a 2 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6NX8 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6NX8 FirstGlance]. <br>
<table><tr><td colspan='2'>[[6nx8]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Ecoli Ecoli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6NX8 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6NX8 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=ACY:ACETIC+ACID'>ACY</scene>, <scene name='pdbligand=CIT:CITRIC+ACID'>CIT</scene></td></tr>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=ACY:ACETIC+ACID'>ACY</scene>, <scene name='pdbligand=CIT:CITRIC+ACID'>CIT</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[6nx6|6nx6]], [[6nx7|6nx7]], [[6nx9|6nx9]], [[6nxa|6nxa]], [[6nxb|6nxb]], [[6nxc|6nxc]], [[6nxd|6nxd]]</td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[6nx6|6nx6]], [[6nx7|6nx7]], [[6nx9|6nx9]], [[6nxa|6nxa]], [[6nxb|6nxb]], [[6nxc|6nxc]], [[6nxd|6nxd]]</td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">ansB, b2957, JW2924 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=83333 ECOLI])</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Asparaginase Asparaginase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.1.1 3.5.1.1] </span></td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Asparaginase Asparaginase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.1.1 3.5.1.1] </span></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6nx8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6nx8 OCA], [http://pdbe.org/6nx8 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=6nx8 RCSB], [http://www.ebi.ac.uk/pdbsum/6nx8 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=6nx8 ProSAT]</span></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=6nx8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6nx8 OCA], [http://pdbe.org/6nx8 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=6nx8 RCSB], [http://www.ebi.ac.uk/pdbsum/6nx8 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=6nx8 ProSAT]</span></td></tr>
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<div style="background-color:#fffaf0;">
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
AnsA is the cytoplasmic asparaginase from Escherichia coli involved in intracellular asparagine utilization. Analytical ultracentifugation and X-ray crystallography reveal that AnsA forms a tetrameric structure as a dimer of two intimate dimers. Kinetic analysis of the enzyme reveals that AnsA is positively cooperative, displaying a sigmoidal substrate dependence curve with an [S](0.5) of 1 mM L-asparagine and a Hill coefficient (n(H)) of 2.6. Binding of L-asparagine to an allosteric site was observed in the crystal structure concomitant with a reorganization of the quarternary structure, relative to the apo enzyme. The carboxyl group of the bound asparagine makes salt bridges and hydrogen bonds to Arg240, while the N(delta2) nitrogen interacts with Thr162. Mutation of Arg240 to Ala increases the [S](0.5) value to 5.9 mM, presumably by reducing the affinity of the site for L-asparagine, although the enzyme retains cooperativity. Mutation of Thr162 to Ala results in an active enzyme with no cooperativity. Transmission of the signal from the allosteric site to the active site appears to involve subtle interactions at the dimer-dimer interface and relocation of Gln118 into the vicinity of the active site to position the probable catalytic water molecule. These data define the structural basis for the cooperative regulation of the intracellular asparaginase that is required for proper functioning within the cell.
Active sites of enzymes are highly optimized for interactions with specific substrates, thus binding of opportunistic ligands is usually observed only in the absence of native substrates or products. However, during growth of crystals required for structure determination enzymes are often exposed to conditions significantly divergent from the native ones, leading to binding of unexpected ligands to active sites even in the presence of substrates. Failing to recognize this possibility may lead to incorrect interpretation of experimental results and to faulty conclusions. Here, we present several examples of binding of a citrate anion to the active sites of E. coli L-asparaginases I and II, even in the presence of the native substrate, L-Asn. A part of this report focuses on a comprehensive re-interpretation of structural results published previously for complexes of type I L-asparaginase (EcAI) from E. coli. In two re-refined structures a citrate anion forms an acyl-enzyme reaction intermediate with the catalytic threonine. These results emphasize the importance of careful and critical analysis during interpretation of crystallographic data.


Crystal structure and allosteric regulation of the cytoplasmic Escherichia coli L-asparaginase I.,Yun MK, Nourse A, White SW, Rock CO, Heath RJ J Mol Biol. 2007 Jun 8;369(3):794-811. Epub 2007 Mar 30. PMID:17451745<ref>PMID:17451745</ref>
Opportunistic complexes of E. coli L-asparaginases with citrate anions.,Lubkowski J, Chan W, Wlodawer A Sci Rep. 2019 Jul 30;9(1):11070. doi: 10.1038/s41598-019-46432-0. PMID:31363102<ref>PMID:31363102</ref>


From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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</StructureSection>
</StructureSection>
[[Category: Asparaginase]]
[[Category: Asparaginase]]
[[Category: Ecoli]]
[[Category: Large Structures]]
[[Category: Large Structures]]
[[Category: Lubkowski, J]]
[[Category: Lubkowski, J]]

Revision as of 20:39, 20 November 2019

ECAII(T89V,K162T) MUTANT IN COMPLEX WITH CITRATE AT PH 6.2ECAII(T89V,K162T) MUTANT IN COMPLEX WITH CITRATE AT PH 6.2

Structural highlights

6nx8 is a 2 chain structure with sequence from Ecoli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Ligands:,
Gene:ansB, b2957, JW2924 (ECOLI)
Activity:Asparaginase, with EC number 3.5.1.1
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Publication Abstract from PubMed

Active sites of enzymes are highly optimized for interactions with specific substrates, thus binding of opportunistic ligands is usually observed only in the absence of native substrates or products. However, during growth of crystals required for structure determination enzymes are often exposed to conditions significantly divergent from the native ones, leading to binding of unexpected ligands to active sites even in the presence of substrates. Failing to recognize this possibility may lead to incorrect interpretation of experimental results and to faulty conclusions. Here, we present several examples of binding of a citrate anion to the active sites of E. coli L-asparaginases I and II, even in the presence of the native substrate, L-Asn. A part of this report focuses on a comprehensive re-interpretation of structural results published previously for complexes of type I L-asparaginase (EcAI) from E. coli. In two re-refined structures a citrate anion forms an acyl-enzyme reaction intermediate with the catalytic threonine. These results emphasize the importance of careful and critical analysis during interpretation of crystallographic data.

Opportunistic complexes of E. coli L-asparaginases with citrate anions.,Lubkowski J, Chan W, Wlodawer A Sci Rep. 2019 Jul 30;9(1):11070. doi: 10.1038/s41598-019-46432-0. PMID:31363102[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

  1. Lubkowski J, Chan W, Wlodawer A. Opportunistic complexes of E. coli L-asparaginases with citrate anions. Sci Rep. 2019 Jul 30;9(1):11070. doi: 10.1038/s41598-019-46432-0. PMID:31363102 doi:http://dx.doi.org/10.1038/s41598-019-46432-0

6nx8, resolution 1.85Å

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