1ga0
From Proteopedia
(New page: 200px<br /><applet load="1ga0" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ga0, resolution 1.6Å" /> '''STRUCTURE OF THE E. C...) |
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| - | [[Image:1ga0.jpg|left|200px]]<br /><applet load="1ga0" size=" | + | [[Image:1ga0.jpg|left|200px]]<br /><applet load="1ga0" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1ga0, resolution 1.6Å" /> | caption="1ga0, resolution 1.6Å" /> | ||
'''STRUCTURE OF THE E. CLOACAE GC1 BETA-LACTAMASE WITH A CEPHALOSPORIN SULFONE INHIBITOR'''<br /> | '''STRUCTURE OF THE E. CLOACAE GC1 BETA-LACTAMASE WITH A CEPHALOSPORIN SULFONE INHIBITOR'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The crystallographic structure of the Enterobacter cloacae GC1 | + | The crystallographic structure of the Enterobacter cloacae GC1 extended-spectrum class C beta-lactamase, inhibited by a new 7-alkylidenecephalosporin sulfone, has been determined by X-ray diffraction at 100 K to a resolution of 1.6 A. The crystal structure was solved by molecular replacement using the unliganded structure [Crichlow et al. (1999) Biochemistry 38, 10256-10261] and refined to a crystallographic R-factor equal to 0.183 (R(free) 0.208). Cryoquenching of the reaction of the sulfone with the enzyme produced an intermediate that is covalently bound via Ser64. After acylation of the beta-lactam ring, the dihydrothiazine dioxide ring opened with departure of the sulfinate. Nucleophilic attack of a side chain pyridine nitrogen atom on the C6 atom of the resultant imine yielded a bicyclic aromatic system which helps to stabilize the acyl enzyme to hydrolysis. A structural assist to this resonance stabilization is the positioning of the anionic sulfinate group between the probable catalytic base (Tyr150) and the acyl ester bond so as to block the approach of a potentially deacylating water molecule. Comparison of the liganded and unliganded protein structures showed that a major movement (up to 7 A) and refolding of part of the Omega-loop (215-224) accompanies the binding of the inhibitor. This conformational flexibility in the Omega-loop may form the basis of an extended-spectrum activity of class C beta-lactamases against modern cephalosporins. |
==About this Structure== | ==About this Structure== | ||
| - | 1GA0 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Enterobacter_cloacae Enterobacter cloacae] with NA, DVR and GOL 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:// | + | 1GA0 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Enterobacter_cloacae Enterobacter cloacae] with <scene name='pdbligand=NA:'>NA</scene>, <scene name='pdbligand=DVR:'>DVR</scene> and <scene name='pdbligand=GOL:'>GOL</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=1GA0 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Enterobacter cloacae]] | [[Category: Enterobacter cloacae]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Buynak, J | + | [[Category: Buynak, J D.]] |
| - | [[Category: Crichlow, G | + | [[Category: Crichlow, G V.]] |
| - | [[Category: Knox, J | + | [[Category: Knox, J R.]] |
[[Category: Nukaga, M.]] | [[Category: Nukaga, M.]] | ||
[[Category: DVR]] | [[Category: DVR]] | ||
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[[Category: mixed alpha/beta]] | [[Category: mixed alpha/beta]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:47:49 2008'' |
Revision as of 10:47, 21 February 2008
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STRUCTURE OF THE E. CLOACAE GC1 BETA-LACTAMASE WITH A CEPHALOSPORIN SULFONE INHIBITOR
Overview
The crystallographic structure of the Enterobacter cloacae GC1 extended-spectrum class C beta-lactamase, inhibited by a new 7-alkylidenecephalosporin sulfone, has been determined by X-ray diffraction at 100 K to a resolution of 1.6 A. The crystal structure was solved by molecular replacement using the unliganded structure [Crichlow et al. (1999) Biochemistry 38, 10256-10261] and refined to a crystallographic R-factor equal to 0.183 (R(free) 0.208). Cryoquenching of the reaction of the sulfone with the enzyme produced an intermediate that is covalently bound via Ser64. After acylation of the beta-lactam ring, the dihydrothiazine dioxide ring opened with departure of the sulfinate. Nucleophilic attack of a side chain pyridine nitrogen atom on the C6 atom of the resultant imine yielded a bicyclic aromatic system which helps to stabilize the acyl enzyme to hydrolysis. A structural assist to this resonance stabilization is the positioning of the anionic sulfinate group between the probable catalytic base (Tyr150) and the acyl ester bond so as to block the approach of a potentially deacylating water molecule. Comparison of the liganded and unliganded protein structures showed that a major movement (up to 7 A) and refolding of part of the Omega-loop (215-224) accompanies the binding of the inhibitor. This conformational flexibility in the Omega-loop may form the basis of an extended-spectrum activity of class C beta-lactamases against modern cephalosporins.
About this Structure
1GA0 is a Single protein structure of sequence from Enterobacter cloacae with , and as ligands. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
Inhibition of class C beta-lactamases: structure of a reaction intermediate with a cephem sulfone., Crichlow GV, Nukaga M, Doppalapudi VR, Buynak JD, Knox JR, Biochemistry. 2001 May 29;40(21):6233-9. PMID:11371184
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