View source for 3ixh

==X-ray crystal structure of the extended-spectrum AmpC Y221G mutant beta-lactamase in complex with cefotaxime at 2.3 Angstrom resolution==
<StructureSection load='3ixh' size='340' side='right' caption='[[3ixh]], [[Resolution|resolution]] 2.30&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3ixh]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3IXH OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3IXH FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=PCZ:(2R)-2-[(1R)-1-{[(2Z)-2-(2-AMINO-1,3-THIAZOL-4-YL)-2-(METHOXYIMINO)ACETYL]AMINO}-2-OXOETHYL]-5-METHYLIDENE-5,6-DIHYDRO-2H-1,3-THIAZINE-4-CARBOXYLIC+ACID'>PCZ</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[3iwi|3iwi]], [[3iwo|3iwo]], [[3iwq|3iwq]], [[3ixb|3ixb]], [[3ixd|3ixd]], [[3ixg|3ixg]]</td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">ampA, ampC, b4150, JW4111 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=562 Escherichia coli])</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Beta-lactamase Beta-lactamase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.2.6 3.5.2.6] </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=3ixh FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3ixh OCA], [http://www.rcsb.org/pdb/explore.do?structureId=3ixh RCSB], [http://www.ebi.ac.uk/pdbsum/3ixh PDBsum]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/AMPC_ECOLI AMPC_ECOLI]] This protein is a serine beta-lactamase with a substrate specificity for cephalosporins. 
== 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/ix/3ixh_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 ==
Preorganization of enzyme active sites for substrate recognition typically comes at a cost to the stability of the folded form of the protein; consequently, enzymes can be dramatically stabilized by substitutions that attenuate the size and preorganization "strain" of the active site. How this stability-activity tradeoff constrains enzyme evolution has remained less certain, and it is unclear whether one should expect major stability insults as enzymes mutate towards new activities or how these new activities manifest structurally. These questions are both germane and easy to study in beta-lactamases, which are evolving on the timescale of years to confer resistance to an ever-broader spectrum of beta-lactam antibiotics. To explore whether stability is a substantial constraint on this antibiotic resistance evolution, we investigated extended-spectrum mutants of class C beta-lactamases, which had evolved new activity versus third-generation cephalosporins. Five mutant enzymes had between 100-fold and 200-fold increased activity against the antibiotic cefotaxime in enzyme assays, and the mutant enzymes all lost thermodynamic stability (from 1.7 kcal mol(-)(1) to 4.1 kcal mol(-)(1)), consistent with the stability-function hypothesis. Intriguingly, several of the substitutions were 10-20 A from the catalytic serine; the question of how they conferred extended-spectrum activity arose. Eight structures, including complexes with inhibitors and extended-spectrum antibiotics, were determined by X-ray crystallography. Distinct mechanisms of action, including changes in the flexibility and ground-state structures of the enzyme, are revealed for each mutant. These results explain the structural bases for the antibiotic resistance conferred by these substitutions and their corresponding decrease in protein stability, which will constrain the evolution of new antibiotic resistance.

Structural bases for stability-function tradeoffs in antibiotic resistance.,Thomas VL, McReynolds AC, Shoichet BK J Mol Biol. 2010 Feb 12;396(1):47-59. Epub 2009 Nov 10. PMID:19913034<ref>PMID:19913034</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>

==See Also==
*[[Beta-lactamase|Beta-lactamase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Beta-lactamase]]
[[Category: Escherichia coli]]
[[Category: Shoichet, B K]]
[[Category: Thomas, V L]]
[[Category: Antibiotic resistance]]
[[Category: Cephalosporinase]]
[[Category: Extended-spectrum antibiotic resistance]]
[[Category: Hydrolase]]
[[Category: Serine hydrolase]]