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[[Image:1yfd.gif|left|200px]]
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[[Image:1yfd.png|left|200px]]


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{{STRUCTURE_1yfd|  PDB=1yfd  |  SCENE=  }}  
{{STRUCTURE_1yfd|  PDB=1yfd  |  SCENE=  }}  


'''Crystal structure of the Y122H mutant of ribonucleotide reductase R2 protein from E. coli'''
===Crystal structure of the Y122H mutant of ribonucleotide reductase R2 protein from E. coli===




==Overview==
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The R2 protein subunit of class I ribonucleotide reductase (RNR) belongs to a structurally related family of oxygen bridged diiron proteins. In wild-type R2 of Escherichia coli, reductive cleavage of molecular oxygen by the diferrous iron center generates a radical on a nearby tyrosine residue (Tyr122), which is essential for the enzymatic activity of RNR, converting ribonucleotides into deoxyribonucleotides. In this work, we characterize the mutant E. coli protein R2-Y122H, where the radical site is substituted with a histidine residue. The x-ray structure verifies the mutation. R2-Y122H contains a novel stable paramagnetic center which we name H, and which we have previously proposed to be a diferric iron center with a strongly coupled radical, Fe(III)Fe(III)R.. Here we report a detailed characterization of center H, using 1H/2H -14N/15N- and 57Fe-ENDOR in comparison with the Fe(III)Fe(IV) intermediate X observed in the iron reconstitution reaction of R2. Specific deuterium labeling of phenylalanine residues reveals that the radical results from a phenylalanine. As Phe208 is the only phenylalanine in the ligand sphere of the iron site, and generation of a phenyl radical requires a very high oxidation potential, we propose that in Y122H residue Phe208 is hydroxylated, as observed earlier in another mutant (R2-Y122F/E238A), and further oxidized to a phenoxyl radical, which is coordinated to Fe1. This work demonstrates that small structural changes can redirect the reactivity of the diiron site, leading to oxygenation of a hydrocarbon, as observed in the structurally similar methane monoxygenase, and beyond, to formation of a stable iron-coordinated radical.
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{{ABSTRACT_PUBMED_15634667}}


==About this Structure==
==About this Structure==
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[[Category: Sjoeberg, B M.]]
[[Category: Sjoeberg, B M.]]
[[Category: Di-iron center]]
[[Category: Di-iron center]]
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Revision as of 08:23, 28 July 2008

File:1yfd.png

Template:STRUCTURE 1yfd

Crystal structure of the Y122H mutant of ribonucleotide reductase R2 protein from E. coli

Template:ABSTRACT PUBMED 15634667

About this Structure

1YFD is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

A new tyrosyl radical on Phe208 as ligand to the diiron center in Escherichia coli ribonucleotide reductase, mutant R2-Y122H. Combined x-ray diffraction and EPR/ENDOR studies., Kolberg M, Logan DT, Bleifuss G, Potsch S, Sjoberg BM, Graslund A, Lubitz W, Lassmann G, Lendzian F, J Biol Chem. 2005 Mar 25;280(12):11233-46. Epub 2005 Jan 5. PMID:15634667

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