R2 subunit of ribonucleotide reductase

Interest in this class of coordination compounds was sparked and fueled by the discovery that radical cofactors such as tyrosyl radicals play an important role in a rapidly growing number of metalloproteins. Thus, in 1972 Ehrenberg and Reichard (1) discovered that the R2 subunit of ribonucleotide reductase, a non-heme metal-loprotein, contains an uncoordinated, very stable tyrosyl radical in its active site. In contrast, Whittaker and Whittaker (2) showed that the active site of the copper containing enzyme galactose oxidase (GO) contains a radical cofactor where a Cu(II) ion is coordinated to a tyrosyl radical. 

Andersson, M. E., H"gbom, M., Rinaldo-Matthis, A., Andersson, K. K., Sj berg, B.-M., and Nordlund, P., 1999, The crystal structnre of an azide complex of the diferrous R2 subunit of ribonucleotide reductase displays a novel carboxylate shift with important mechanistic implications for diiron-catalyzed oxygen activation. J. Amer. Chem. Soc. 121 2346n2352. 

Atta, M., Andersson, K. K., Ingemarson, R., Thelander, L., and Gr%oslund, A., 1994, EPR studies of mixed-valent [Fe Fe ] clusters formed in the R2 subunit of ribonucleotide reductase from mouse or herpes simplex virus Mild chemical reduction of the diferric centers. J. Am. Chem. Soc. 116 6429n6430. 

Scheme 1 Reaction cycle for R2 subunit of ribonucleotide reductase...

Figure 7. Resonance Raman spectra of [Fe2O(XDK)(BIDPhE)2(N03)2] and the R2 subunit of ribonucleotide reductase.

GaUi C, Atta M, Andersson KK, Graslund A, Brudvig GW. 1995. Variations of the diferric exchange coupling in the R2 subunit of ribonucleotide reductase from four species as determined by saturation-recovery EPR spectroscopy. J Am Chem Soc 117 740-746. 

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