1fr6
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(New page: 200px<br /><applet load="1fr6" size="450" color="white" frame="true" align="right" spinBox="true" caption="1fr6, resolution 2.5Å" /> '''REFINED CRYSTAL STRUC...)
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Revision as of 22:08, 24 November 2007
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REFINED CRYSTAL STRUCTURE OF BETA-LACTAMASE FROM CITROBACTER FREUNDII INDICATES A MECHANISM FOR BETA-LACTAM HYDROLYSIS
Overview
Beta-Lactamases (EC 3.5.2.6, 'penicillinases') are a family of enzymes, that protect bacteria against the lethal effects of cell-wall synthesis of, penicillins, cephalosporins and related antibiotic agents, by hydrolysing, the beta-lactam antibiotics to biologically inactive compounds. Their, production can, therefore, greatly contribute to the clinical problem of, antibiotic resistance. Three classes of beta-lactamases--A, B and C--have, been identified on the basis of their amino-acid sequence; class B, beta-lactamases are metalloenzymes, and are clearly distinct from members, of class A and C beta-lactamases, which both contain an active-site serine, residue involved in the formation of an acyl enzyme with beta-lactam, substrates during catalysis. It has been predicted that class C, beta-lactamases share common structural features with, D,D-carboxypeptidases and class A beta-lactamases, and further, suggested, that class A and class C beta-lactamases have the same evolutionary origin, as other beta-lactam target enzymes. We report here the refined, three-dimensional structure of the class C beta-lactamase from Citrobacter, freundii at 2.0-A resolution and confirm the predicted structural, similarity. The refined structure of the acyl-enzyme formed with the, monobactam inhibitor aztreonam at 2.5-A resolution defines the enzyme's, active site and, along with molecular modelling, indicates a mechanism for, beta-lactam hydrolysis. This leads to the hypothesis that Tyr 150, functions as a general base during catalysis.
About this Structure
1FR6 is a Single protein structure of sequence from Citrobacter freundii with AZR as ligand. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
Refined crystal structure of beta-lactamase from Citrobacter freundii indicates a mechanism for beta-lactam hydrolysis., Oefner C, D'Arcy A, Daly JJ, Gubernator K, Charnas RL, Heinze I, Hubschwerlen C, Winkler FK, Nature. 1990 Jan 18;343(6255):284-8. PMID:2300174
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