1jpr
Mn substituted Ribonucleotide reductase R2 from E. coli oxidized by nitric oxide
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OverviewOverview
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 StructureAbout this Structure
1JPR is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Ribonucleoside-diphosphate reductase, with EC number 1.17.4.1 Full crystallographic information is available from OCA.
ReferenceReference
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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