1jqc
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(New page: 200px<br /><applet load="1jqc" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jqc, resolution 1.61Å" /> '''Mn substituted Ribon...)
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Revision as of 16:21, 20 November 2007
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Mn substituted Ribonucleotide reductase R2 from E. Coli oxidized by hydrogen peroxide and hydroxylamine
Overview
The di-iron carboxylate proteins constitute a diverse class of non-heme, iron enzymes performing a multitude of redox reactions. These reactions, usually involve high-valent Fe-oxo species and are thought to be, controlled by carboxylate shifts. Owing to their short lifetime, the, intermediate structures have so far escaped structural characterization by, X-ray crystallography. In an attempt to map the carboxylate conformations, available to the protein during different redox states and different, ligand environments, we have studied metal-substituted forms of the R2, protein of ribonucleotide reductase from Escherichia coli. In the present, work we have solved the crystal structures of Mn-substituted R2 oxidized, in two different ways. Oxidation was performed using either nitric oxide, or a combination of hydrogen peroxide and hydroxylamine. The two, structures are virtually identical, indicating that the oxidation states, are the same, most likely a mixed-valent MnII-MnIII centre. One of the, carboxylate ligands (D84) adopts a new, so far unseen, conformation, which, could participate in the mechanism for radical generation in R2. E238, adopts a bridging-chelating conformation proposed to be important for, proper O2 activation but not previously observed in the wild-type enzyme., Probable catalase activity was also observed during the oxidation with, H2O2, indicating mechanistic similarities to the di-Mn catalases.
About this Structure
1JQC is a Single protein structure of sequence from Escherichia coli with MN and HG as ligands. Active as Ribonucleoside-diphosphate reductase, with EC number 1.17.4.1 Full crystallographic information is available from OCA.
Reference
Crystal structures of oxidized dinuclear manganese centres in Mn-substituted class I ribonucleotide reductase from Escherichia coli: carboxylate shifts with implications for O2 activation and radical generation., Hogbom M, Andersson ME, Nordlund P, J Biol Inorg Chem. 2001 Mar;6(3):315-23. PMID:11315567
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