1sml
From Proteopedia
(New page: 200px<br /><applet load="1sml" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sml, resolution 1.7Å" /> '''METALLO BETA LACTAMAS...) |
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| - | [[Image:1sml.gif|left|200px]]<br /><applet load="1sml" size=" | + | [[Image:1sml.gif|left|200px]]<br /><applet load="1sml" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1sml, resolution 1.7Å" /> | caption="1sml, resolution 1.7Å" /> | ||
'''METALLO BETA LACTAMASE L1 FROM STENOTROPHOMONAS MALTOPHILIA'''<br /> | '''METALLO BETA LACTAMASE L1 FROM STENOTROPHOMONAS MALTOPHILIA'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The structure of the L1 metallo-beta-lactamase from the opportunistic | + | The structure of the L1 metallo-beta-lactamase from the opportunistic pathogen Stenotrophomonas maltophilia has been determined at 1.7 A resolution by the multiwavelength anomalous dispersion (MAD) approach exploiting both the intrinsic binuclear zinc centre and incorporated selenomethionine residues. L1 is unique amongst all known beta-lactamases in that it exists as a tetramer. The protein exhibits the alphabeta/betaalpha fold found only in the metallo-beta-lactamases and displays several unique features not previously observed in these enzymes. These include a disulphide bridge and two substantially elongated loops connected to the active site of the enzyme. Two closely spaced zinc ions are bound at the active site with tetrahedral (Zn1) and trigonal bipyramidal (Zn2) co-ordination, respectively; these are bridged by a water molecule which we propose acts as the nucleophile in the hydrolytic reaction. Ligation of the second zinc ion involves both residues and geometry which have not been previously observed in the metallo-beta-lactamases. Simulated binding of the substrates ampicillin, ceftazidime and imipenem suggests that the substrate is able to bind to the enzyme in a variety of different conformations whose common features are direct interactions of the beta-lactam carbonyl oxygen and nitrogen with the zinc ions and of the beta-lactam carboxylate with Ser187. We describe a catalytic mechanism whose principal features are a nucleophilic attack of the bridging water on the beta-lactam carbonyl carbon, electrostatic stabilisation of a negatively charged tetrahedral transition state and protonation of the beta-lactam nitrogen by a second water molecule co-ordinated by Zn2. Further, we propose that direct metal:substrate interactions provide a substantial contribution to substrate binding and that this may explain the lack of specificity which is a feature of this class of enzyme. |
==About this Structure== | ==About this Structure== | ||
| - | 1SML is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Stenotrophomonas_maltophilia Stenotrophomonas maltophilia] with ZN as [http://en.wikipedia.org/wiki/ligand ligand]. 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:// | + | 1SML is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Stenotrophomonas_maltophilia Stenotrophomonas maltophilia] with <scene name='pdbligand=ZN:'>ZN</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. 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=1SML OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Stenotrophomonas maltophilia]] | [[Category: Stenotrophomonas maltophilia]] | ||
| - | [[Category: Emery, D | + | [[Category: Emery, D C.]] |
| - | [[Category: Gamblin, S | + | [[Category: Gamblin, S J.]] |
[[Category: Spencer, J.]] | [[Category: Spencer, J.]] | ||
| - | [[Category: Taylor, I | + | [[Category: Taylor, I A.]] |
| - | [[Category: Ullah, J | + | [[Category: Ullah, J H.]] |
| - | [[Category: Verma, C | + | [[Category: Verma, C S.]] |
| - | [[Category: Walsh, T | + | [[Category: Walsh, T R.]] |
[[Category: ZN]] | [[Category: ZN]] | ||
[[Category: antibiotic resistance]] | [[Category: antibiotic resistance]] | ||
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[[Category: metallo-beta-lactamase]] | [[Category: metallo-beta-lactamase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:03:02 2008'' |
Revision as of 13:03, 21 February 2008
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METALLO BETA LACTAMASE L1 FROM STENOTROPHOMONAS MALTOPHILIA
Overview
The structure of the L1 metallo-beta-lactamase from the opportunistic pathogen Stenotrophomonas maltophilia has been determined at 1.7 A resolution by the multiwavelength anomalous dispersion (MAD) approach exploiting both the intrinsic binuclear zinc centre and incorporated selenomethionine residues. L1 is unique amongst all known beta-lactamases in that it exists as a tetramer. The protein exhibits the alphabeta/betaalpha fold found only in the metallo-beta-lactamases and displays several unique features not previously observed in these enzymes. These include a disulphide bridge and two substantially elongated loops connected to the active site of the enzyme. Two closely spaced zinc ions are bound at the active site with tetrahedral (Zn1) and trigonal bipyramidal (Zn2) co-ordination, respectively; these are bridged by a water molecule which we propose acts as the nucleophile in the hydrolytic reaction. Ligation of the second zinc ion involves both residues and geometry which have not been previously observed in the metallo-beta-lactamases. Simulated binding of the substrates ampicillin, ceftazidime and imipenem suggests that the substrate is able to bind to the enzyme in a variety of different conformations whose common features are direct interactions of the beta-lactam carbonyl oxygen and nitrogen with the zinc ions and of the beta-lactam carboxylate with Ser187. We describe a catalytic mechanism whose principal features are a nucleophilic attack of the bridging water on the beta-lactam carbonyl carbon, electrostatic stabilisation of a negatively charged tetrahedral transition state and protonation of the beta-lactam nitrogen by a second water molecule co-ordinated by Zn2. Further, we propose that direct metal:substrate interactions provide a substantial contribution to substrate binding and that this may explain the lack of specificity which is a feature of this class of enzyme.
About this Structure
1SML is a Single protein structure of sequence from Stenotrophomonas maltophilia with as ligand. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
The crystal structure of the L1 metallo-beta-lactamase from Stenotrophomonas maltophilia at 1.7 A resolution., Ullah JH, Walsh TR, Taylor IA, Emery DC, Verma CS, Gamblin SJ, Spencer J, J Mol Biol. 1998 Nov 20;284(1):125-36. PMID:9811546
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