1rsv
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azide complex of the diferrous E238A mutant R2 subunit of ribonucleotide reductase
OverviewOverview
The enzyme activity of Escherichia coli ribonucleotide reductase requires, the presence of a stable tyrosyl free radical and diiron center in its, smaller R2 component. The iron/radical site is formed in a reconstitution, reaction between ferrous iron and molecular oxygen in the protein. The, reaction is known to proceed via a paramagnetic intermediate X, formally a, Fe(III)-Fe(IV) state. We have used 9.6 GHz and 285 GHz EPR to investigate, intermediates in the reconstitution reaction in the iron ligand mutant R2, E238A with or without azide, formate, or acetate present. Paramagnetic, intermediates, i.e. a long-living X-like intermediate and a transient, tyrosyl radical, were observed only with azide and under none of the other, conditions. A crystal structure of the mutant protein R2 E238A/Y122F with, a diferrous iron site complexed with azide was determined. Azide was found, to be a bridging ligand and the absent Glu-238 ligand was compensated for, by azide and an extra coordination from Glu-204. A general scheme for the, reconstitution reaction is presented based on EPR and structure results., This indicates that tyrosyl radical generation requires a specific ligand, coordination with 4-coordinate Fe1 and 6-coordinate Fe2 after oxygen, binding to the diferrous site.
About this StructureAbout this Structure
1RSV is a Single protein structure of sequence from Escherichia coli with FE, HG and AZI as ligands. Active as Ribonucleoside-diphosphate reductase, with EC number 1.17.4.1 Full crystallographic information is available from OCA.
ReferenceReference
Restoring proper radical generation by azide binding to the iron site of the E238A mutant R2 protein of ribonucleotide reductase from Escherichia coli., Assarsson M, Andersson ME, Hogbom M, Persson BO, Sahlin M, Barra AL, Sjoberg BM, Nordlund P, Graslund A, J Biol Chem. 2001 Jul 20;276(29):26852-9. Epub 2001 Apr 27. PMID:11328804
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