1iel
From Proteopedia
(New page: 200px<br /><applet load="1iel" size="450" color="white" frame="true" align="right" spinBox="true" caption="1iel, resolution 2.00Å" /> '''Crystal Structure of...) |
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| - | [[Image:1iel.gif|left|200px]]<br /><applet load="1iel" size=" | + | [[Image:1iel.gif|left|200px]]<br /><applet load="1iel" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1iel, resolution 2.00Å" /> | caption="1iel, resolution 2.00Å" /> | ||
'''Crystal Structure of AmpC beta-lactamase from E. coli in Complex with Ceftazidime'''<br /> | '''Crystal Structure of AmpC beta-lactamase from E. coli in Complex with Ceftazidime'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Third-generation cephalosporins are widely used beta-lactam antibiotics | + | Third-generation cephalosporins are widely used beta-lactam antibiotics that resist hydrolysis by beta-lactamases. Recently, mutant beta-lactamases that rapidly inactivate these drugs have emerged. To investigate why third-generation cephalosporins are relatively stable to wild-type class C beta-lactamases and how mutant enzymes might overcome this, the structures of the class C beta-lactamase AmpC in complex with the third-generation cephalosporin ceftazidime and with a transition-state analogue of ceftazidime were determined by X-ray crystallography to 2.0 and 2.3 A resolution, respectively. Comparison of the acyl-enzyme structures of ceftazidime and loracarbef, a beta-lactam substrate, reveals that the conformation of ceftazidime in the active site differs from that of substrates. Comparison of the structures of the acyl-enzyme intermediate and the transition-state analogue suggests that ceftazidime blocks formation of the tetrahedral transition state, explaining why it is an inhibitor of AmpC. Ceftazidime cannot adopt a conformation competent for catalysis due to steric clashes that would occur with conserved residues Val211 and Tyr221. The X-ray crystal structure of the mutant beta-lactamase GC1, which has improved activity against third-generation cephalosporins, suggests that a tandem tripeptide insertion in the Omega loop, which contains Val211, has caused a shift of this residue and also of Tyr221 that would allow ceftazidime and other third-generation cephalosporins to adopt a more catalytically competent conformation. These structural differences may explain the extended spectrum activity of GC1 against this class of cephalosporins. In addition, the complexed structure of the transition-state analogue inhibitor (K(i) 20 nM) with AmpC reveals potential opportunities for further inhibitor design. |
==About this Structure== | ==About this Structure== | ||
| - | 1IEL 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 PO4 and CAZ as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http:// | + | 1IEL 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=PO4:'>PO4</scene> and <scene name='pdbligand=CAZ:'>CAZ</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IEL OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Caselli, E.]] | [[Category: Caselli, E.]] | ||
| - | [[Category: Focia, P | + | [[Category: Focia, P J.]] |
| - | [[Category: Powers, R | + | [[Category: Powers, R A.]] |
[[Category: Prati, F.]] | [[Category: Prati, F.]] | ||
| - | [[Category: Shoichet, B | + | [[Category: Shoichet, B K.]] |
[[Category: CAZ]] | [[Category: CAZ]] | ||
[[Category: PO4]] | [[Category: PO4]] | ||
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[[Category: serine hydrolase]] | [[Category: serine hydrolase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:11:03 2008'' |
Revision as of 11:11, 21 February 2008
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Crystal Structure of AmpC beta-lactamase from E. coli in Complex with Ceftazidime
Overview
Third-generation cephalosporins are widely used beta-lactam antibiotics that resist hydrolysis by beta-lactamases. Recently, mutant beta-lactamases that rapidly inactivate these drugs have emerged. To investigate why third-generation cephalosporins are relatively stable to wild-type class C beta-lactamases and how mutant enzymes might overcome this, the structures of the class C beta-lactamase AmpC in complex with the third-generation cephalosporin ceftazidime and with a transition-state analogue of ceftazidime were determined by X-ray crystallography to 2.0 and 2.3 A resolution, respectively. Comparison of the acyl-enzyme structures of ceftazidime and loracarbef, a beta-lactam substrate, reveals that the conformation of ceftazidime in the active site differs from that of substrates. Comparison of the structures of the acyl-enzyme intermediate and the transition-state analogue suggests that ceftazidime blocks formation of the tetrahedral transition state, explaining why it is an inhibitor of AmpC. Ceftazidime cannot adopt a conformation competent for catalysis due to steric clashes that would occur with conserved residues Val211 and Tyr221. The X-ray crystal structure of the mutant beta-lactamase GC1, which has improved activity against third-generation cephalosporins, suggests that a tandem tripeptide insertion in the Omega loop, which contains Val211, has caused a shift of this residue and also of Tyr221 that would allow ceftazidime and other third-generation cephalosporins to adopt a more catalytically competent conformation. These structural differences may explain the extended spectrum activity of GC1 against this class of cephalosporins. In addition, the complexed structure of the transition-state analogue inhibitor (K(i) 20 nM) with AmpC reveals potential opportunities for further inhibitor design.
About this Structure
1IEL is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
Structures of ceftazidime and its transition-state analogue in complex with AmpC beta-lactamase: implications for resistance mutations and inhibitor design., Powers RA, Caselli E, Focia PJ, Prati F, Shoichet BK, Biochemistry. 2001 Aug 7;40(31):9207-14. PMID:11478888
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