1m40
From Proteopedia
(New page: 200px<br /><applet load="1m40" size="450" color="white" frame="true" align="right" spinBox="true" caption="1m40, resolution 0.85Å" /> '''ULTRA HIGH RESOLUTIO...) |
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| - | [[Image:1m40.gif|left|200px]]<br /><applet load="1m40" size=" | + | [[Image:1m40.gif|left|200px]]<br /><applet load="1m40" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1m40, resolution 0.85Å" /> | caption="1m40, resolution 0.85Å" /> | ||
'''ULTRA HIGH RESOLUTION CRYSTAL STRUCTURE OF TEM-1'''<br /> | '''ULTRA HIGH RESOLUTION CRYSTAL STRUCTURE OF TEM-1'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Although TEM-1 beta-lactamase is among the best studied enzymes, its | + | Although TEM-1 beta-lactamase is among the best studied enzymes, its acylation mechanism remains controversial. To investigate this problem, the structure of TEM-1 in complex with an acylation transition-state analogue was determined at ultrahigh resolution (0.85 A) by X-ray crystallography. The quality of the data was such as to allow for refinement to an R-factor of 9.1% and an R(free) of 11.2%. In the resulting structure, the electron density features were clear enough to differentiate between single and double bonds in carboxylate groups, to identify multiple conformations that are occupied by residues and loops, and to assign 70% of the protons in the protein. Unexpectedly, even at pH 8.0 where the protein was crystallized, the active site residue Glu166 is clearly protonated. This supports the hypothesis that Glu166 is the general base in the acylation half of the reaction cycle. This structure suggests that Glu166 acts through the catalytic water to activate Ser70 for nucleophilic attack on the beta-lactam ring of the substrate. The hydrolytic mechanism of class A beta-lactamases, such as TEM-1, appears to be symmetrical, as are the serine proteases. Apart from its mechanistic implications, this atomic resolution structure affords an unusually detailed view of the structure, dynamics, and hydrogen-bonding networks of TEM-1, which may be useful for the design of inhibitors against this key antibiotic resistance target. |
==About this Structure== | ==About this Structure== | ||
| - | 1M40 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, K and CB4 as [http://en.wikipedia.org/wiki/ligands ligands]. This structure | + | 1M40 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>, <scene name='pdbligand=K:'>K</scene> and <scene name='pdbligand=CB4:'>CB4</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. This structure supersedes the now removed PDB entry 1L7U. 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=1M40 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Minasov, G.]] | [[Category: Minasov, G.]] | ||
| - | [[Category: Shoichet, B | + | [[Category: Shoichet, B K.]] |
[[Category: Wang, X.]] | [[Category: Wang, X.]] | ||
[[Category: CB4]] | [[Category: CB4]] | ||
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[[Category: x-ray structure]] | [[Category: x-ray structure]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:51:11 2008'' |
Revision as of 11:51, 21 February 2008
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ULTRA HIGH RESOLUTION CRYSTAL STRUCTURE OF TEM-1
Overview
Although TEM-1 beta-lactamase is among the best studied enzymes, its acylation mechanism remains controversial. To investigate this problem, the structure of TEM-1 in complex with an acylation transition-state analogue was determined at ultrahigh resolution (0.85 A) by X-ray crystallography. The quality of the data was such as to allow for refinement to an R-factor of 9.1% and an R(free) of 11.2%. In the resulting structure, the electron density features were clear enough to differentiate between single and double bonds in carboxylate groups, to identify multiple conformations that are occupied by residues and loops, and to assign 70% of the protons in the protein. Unexpectedly, even at pH 8.0 where the protein was crystallized, the active site residue Glu166 is clearly protonated. This supports the hypothesis that Glu166 is the general base in the acylation half of the reaction cycle. This structure suggests that Glu166 acts through the catalytic water to activate Ser70 for nucleophilic attack on the beta-lactam ring of the substrate. The hydrolytic mechanism of class A beta-lactamases, such as TEM-1, appears to be symmetrical, as are the serine proteases. Apart from its mechanistic implications, this atomic resolution structure affords an unusually detailed view of the structure, dynamics, and hydrogen-bonding networks of TEM-1, which may be useful for the design of inhibitors against this key antibiotic resistance target.
About this Structure
1M40 is a Single protein structure of sequence from Escherichia coli with , and as ligands. This structure supersedes the now removed PDB entry 1L7U. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
An ultrahigh resolution structure of TEM-1 beta-lactamase suggests a role for Glu166 as the general base in acylation., Minasov G, Wang X, Shoichet BK, J Am Chem Soc. 2002 May 15;124(19):5333-40. PMID:11996574
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