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==Acylenzyme complex of ceftazidime bound to deacylation mutant KPC-2 (E166Q)==
<StructureSection load='6z24' size='340' side='right'caption='[[6z24]], [[Resolution|resolution]] 1.25&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6Z24 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6Z24 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]] 1.25&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CAZ:ACYLATED+CEFTAZIDIME'>CAZ</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=6z24 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6z24 OCA], [https://pdbe.org/6z24 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6z24 RCSB], [https://www.ebi.ac.uk/pdbsum/6z24 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6z24 ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
Class A serine beta-lactamases (SBLs) are key antibiotic resistance determinants in Gram-negative bacteria. SBLs neutralize beta-lactams via a hydrolytically labile covalent acyl-enzyme intermediate. Klebsiella pneumoniae carbapenemase (KPC) is a widespread SBL that hydrolyzes carbapenems, the most potent beta-lactams; known KPC variants differ in turnover of expanded-spectrum oxyimino-cephalosporins (ESOCs), e.g. cefotaxime and ceftazidime. Here, we compare ESOC hydrolysis by the parent enzyme KPC-2 and its clinically observed double variant (P104R/V240G) KPC-4. Kinetic analyses show KPC-2 hydrolyzes cefotaxime more efficiently than the bulkier ceftazidime, with improved ESOC turnover by KPC-4 resulting from enhanced turnover (kcat), rather than binding (KM). High-resolution crystal structures of ESOC acyl-enzyme complexes with deacylation-deficient (E166Q) KPC-2 and KPC-4 mutants show that ceftazidime acylation causes rearrangement of three loops; the Omega-, 240- and 270-loops, that border the active site. However, these rearrangements are less pronounced in the KPC-4 than the KPC-2 ceftazidime acyl-enzyme, and are not observed in the KPC-2:cefotaxime acyl-enzyme. Molecular dynamics simulations of KPC:ceftazidime acyl-enyzmes reveal that the deacylation general base E166, located on the Omega-loop, adopts two distinct conformations in KPC-2, either pointing 'in' or 'out' of the active site; with only the 'in' form compatible with deacylation. The 'out' conformation was not sampled in the KPC-4 acyl-enzyme, indicating that efficient ESOC breakdown is dependent upon the ordering and conformation of the KPC Omega-loop. The results explain how point mutations expand the activity spectrum of the clinically important KPC SBLs to include ESOCs through their effects on the conformational dynamics of the acyl-enzyme intermediate.

Natural variants modify Klebsiella pneumoniae carbapenemase (KPC) acyl-enzyme conformational dynamics to extend antibiotic resistance.,Tooke CL, Hinchliffe P, Bonomo RA, Schofield CJ, Mulholland AJ, Spencer J J Biol Chem. 2020 Nov 30. pii: RA120.016461. doi: 10.1074/jbc.RA120.016461. PMID:33257320<ref>PMID:33257320</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Hinchliffe P]]
[[Category: Spencer J]]
[[Category: Tooke CL]]