1m40
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(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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Revision as of 19:00, 20 November 2007
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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 PO4, K and CB4 as ligands. This structure superseeds 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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