1RSV

azide complex of the diferrous E238A mutant R2 subunit of ribonucleotide reductase

Summary for 1RSV

• Entry DOI: 10.2210/pdb1rsv/pdb
• Related: 1mxr 1rsr 1xik
• Descriptor: Ribonucleoside-diphosphate reductase 1 beta chain, FE (III) ION, MERCURY (II) ION, ... (5 entities in total)
• Functional Keywords: diiron, azide, radical generation, chemical rescue, oxidoreductase
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 89378.14

Authors

Assarsson, M.,Andersson, M.E.,Hogbom, M.,Persson, B.O.,Sahlin, M.,Barra, A.L.,Sjoberg, B.M.,Nordlund, P.,Graslund, A. (deposition date: 2003-12-10, release date: 2003-12-23, Last modification date: 2024-05-29)

Primary citation

Assarsson, M.,Andersson, M.E.,Hogbom, M.,Persson, B.O.,Sahlin, M.,Barra, A.L.,Sjoberg, B.M.,Nordlund, P.,Graslund, A.
Restoring proper radical generation by azide binding to the iron site of the E238A mutant R2 protein of ribonucleotide reductase from Escherichia coli.
J.Biol.Chem., 276:26852-26859, 2001

PubMed Abstract: 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.

PubMed: 11328804
DOI: 10.1074/jbc.M008190200

Experimental method

X-RAY DIFFRACTION (2.2 Å)