1qhs
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(New page: 200px<br /><applet load="1qhs" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qhs, resolution 2.8Å" /> '''CHLORAMPHENICOL PHOSP...)
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Revision as of 22:35, 20 November 2007
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CHLORAMPHENICOL PHOSPHOTRANSFERASE IN COMPLEX WITH CHLORAMPHENICOL FROM STREPTOMYCES VENEZUELAE
Overview
Chloramphenicol (Cm), produced by the soil bacterium Streptomyces, venezuelae, is an inhibitor of bacterial ribosomal peptidyltransferase, activity. The Cm-producing streptomycete modifies the primary (C-3), hydroxyl of the antibiotic by a novel Cm-inactivating enzyme, chloramphenicol 3-O-phosphotransferase (CPT). Here we describe the crystal, structures of CPT in the absence and presence of bound substrates. The, enzyme is dimeric in a sulfate-free solution and tetramerization is, induced by ammonium sulfate, the crystallization precipitant. The, tetrameric quaternary structure exhibits crystallographic 222 symmetry and, has ATP binding pockets located at a crystallographic 2-fold axis. Steric, hindrance allows only one ATP to bind per dimer within the tetramer. In, addition to active site binding by Cm, an electron-dense feature, resembling the enzyme's product is found at the other subunit interface., The structures of CPT suggest that an aspartate acts as a general base to, accept a proton from the 3-hydroxyl of Cm, concurrent with nucleophilic, attack of the resulting oxyanion on the gamma-phosphate of ATP. Comparison, between liganded and substrate-free CPT structures highlights side chain, movements of the active site's Arg136 guanidinium group of >9 A upon, substrate binding.
About this Structure
1QHS is a Single protein structure of sequence from Streptomyces venezuelae with SO4 and CLM as ligands. Full crystallographic information is available from OCA.
Reference
The crystal structures of chloramphenicol phosphotransferase reveal a novel inactivation mechanism., Izard T, Ellis J, EMBO J. 2000 Jun 1;19(11):2690-700. PMID:10835366
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