1ejs: Difference between revisions
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[[Image: | ==Crystal Structure of the H219N Variant of Klebsiella Aerogenes Urease== | ||
<StructureSection load='1ejs' size='340' side='right' caption='[[1ejs]], [[Resolution|resolution]] 2.00Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[1ejs]] is a 3 chain structure with sequence from [http://en.wikipedia.org/wiki/Enterobacter_aerogenes Enterobacter aerogenes]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EJS OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1EJS FirstGlance]. <br> | |||
</td></tr><tr><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=NI:NICKEL+(II)+ION'>NI</scene><br> | |||
<tr><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=KCX:LYSINE+NZ-CARBOXYLIC+ACID'>KCX</scene></td></tr> | |||
<tr><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1ejr|1ejr]], [[1ejt|1ejt]], [[1eju|1eju]], [[1ejv|1ejv]], [[1ejw|1ejw]], [[1ejx|1ejx]]</td></tr> | |||
<tr><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Urease Urease], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.1.5 3.5.1.5] </span></td></tr> | |||
<tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1ejs FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ejs OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1ejs RCSB], [http://www.ebi.ac.uk/pdbsum/1ejs PDBsum]</span></td></tr> | |||
<table> | |||
== 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/ej/1ejs_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/chain_selection.php?pdb_ID=2ata ConSurf]. | |||
<div style="clear:both"></div> | |||
<div style="background-color:#fffaf0;"> | |||
== Publication Abstract from PubMed == | |||
Klebsiella aerogenes urease uses a dinuclear nickel active site to catalyze urea hydrolysis at >10(14)-fold the spontaneous rate. To better define the enzyme mechanism, we examined the kinetics and structures for a suite of site-directed variants involving four residues at the active site: His320, His219, Asp221, and Arg336. Compared to wild-type urease, the H320A, H320N, and H320Q variants exhibit similar approximately 10(-)(5)-fold deficiencies in rates, modest K(m) changes, and disorders in the peptide flap covering their active sites. The pH profiles for these mutant enzymes are anomalous with optima near 6 and shoulders that extend to pH 9. H219A urease exhibits 10(3)-fold increased K(m) over that of native enzyme, whereas the increase is less marked ( approximately 10(2)-fold) in the H219N and H219Q variants that retain hydrogen bonding capability. Structures for these variants show clearly resolved active site water molecules covered by well-ordered peptide flaps. Whereas the D221N variant is only moderately affected compared to wild-type enzyme, D221A urease possesses low activity ( approximately 10(-)(3) that of native enzyme), a small increase in K(m), and a pH 5 optimum. The crystal structure for D221A urease is reminiscent of the His320 variants. The R336Q enzyme has a approximately 10(-)(4)-fold decreased catalytic rate with near-normal pH dependence and an unaffected K(m). Phenylglyoxal inactivates the R336Q variant at over half the rate observed for native enzyme, demonstrating that modification of non-active-site arginines can eliminate activity, perhaps by affecting the peptide flap. Our data favor a mechanism in which His219 helps to polarize the substrate carbonyl group, a metal-bound terminal hydroxide or bridging oxo-dianion attacks urea to form a tetrahedral intermediate, and protonation occurs via the general acid His320 with Asp221 and Arg336 orienting and influencing the acidity of this residue. Furthermore, we conclude that the simple bell-shaped pH dependence of k(cat) and k(cat)/K(m) for the native enzyme masks a more complex underlying pH dependence involving at least four pK(a)s. | |||
Kinetic and structural characterization of urease active site variants.,Pearson MA, Park IS, Schaller RA, Michel LO, Karplus PA, Hausinger RP Biochemistry. 2000 Jul 25;39(29):8575-84. PMID:10913264<ref>PMID:10913264</ref> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
</div> | |||
==See Also== | ==See Also== | ||
*[[Urease|Urease]] | *[[Urease|Urease]] | ||
== References == | |||
== | <references/> | ||
< | __TOC__ | ||
</StructureSection> | |||
[[Category: Enterobacter aerogenes]] | [[Category: Enterobacter aerogenes]] | ||
[[Category: Urease]] | [[Category: Urease]] | ||
