ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
SL32. Spectroscopic and Structural Studies of Iron Center and Tyrosyl
Radical in Mammalian, Fish and Bacterial Ribonucleotide Reductase
A.K. Røhr a , A.B. Tomter a ,G.K. Sandvik a , J. Bergan a , A.L. Barra b , G.E. Nilsson . a , K.R.
Strand a , K.K. Andersson a
a Department of Molecular Biosciences, Univ of Oslo, PO Box 1041 Blindern, 0316, Oslo, Norway
b Grenoble High Magnet Field Laboratory GHMFL, CNRS, 25, Rue des Martyres, B.P: 166, FR-38042,
Grenoble, France
e-mail: k.k.andersson@imbv.uio.no
Ribonucleotide reductase (RNR) is the enzyme that converts ribonucleotides to corresponding
deoxyribonucleotides. The R2 subunit of the enzyme complex reacts with ferrous iron and dioxygen to generate
a diferric iron-oxygen cluster and a tyrosyl radical that is essential for enzymatic activity [1]. A p53 induced
isoform of the R2 subunit (p53R2) is proposed to be involved in the production of deoxyribonucleotides for
DNA repair and mitochondrial DNA. The human (Class Ia) R2, bacterial (Class Ib) R2 and murine (Class Ia)
p53R2 proteins have been studied by electron paramagnetic resonance (EPR), magnetic circular dichroism
(MCD) and CD like for mouse R2 [2]. While the studies of the active diferric iron-oxygen cluster and the tyrosyl
radical (also hydrogen binding to the tyrosyl radical) [1, 3, 4] together with the mixed valent form (Fe(II)-Fe(III)
cluster) [3] shows little or no variation between the R2 and p53R2 subunits, also in fish, the MCD and X-band
integer spin EPR studies reveals a difference between the R2 and p53R2 diferrous forms [2] (see also poster by
Ane B. Tomter of Class Ib RNR-R2) and the p53R2 lacks the cooperatively binding of Fe(II) or Co(II) [1, 2, 3,
5, 6]. Taken together the interaction with R1 subunit of RNR are similar for both mammalian and fish R2 and
p53R2 active and possibly mixed valent forms, while the p53R2 do not need to be regulated by cooperatively
binding of Fe(II) as it is induced upon DNA damage [7]. Novel 3D structures have been determined of other
RNR related proteins from B. cereus. In Figure is shown in green diferrous cluster with actetate bound and in red
diferric iron-oxygen cluster demonstrating carboxylate shift in mouse RNR-R2.
References:
[1] Andersson K.K.(ed) Ribonucleotide reductase, Nova Science, 2008, ISBN: 978-1-60456-199-9
[2] Strand, K.R., Yang, Y.-S., Andersson, K.K., Solomon, E.I. Andersson and E.I. Solomon (2003) Circular
dichroism and magnetic circular dichroism studies of the biferrous form of the R2 subunit of ribonucleotide
reductase from mouse. Comparison to the R2 from E. coli and other binuclear ferrous enzymes. Biochemistry,
2003, 42; 12223-12234.
[3] Kolberg M., Strand K.R., Graff P., Andersson K.K. Radicals in Three Different Classes of Ribonucleotide
Reductases: Structural and Functional Basis. Biochim. Biophys. Acta- Proteins and Proteomics, 2004, 1699; 1-
34.
[4] K.K. Andersson, P. P. Schmidt, B. Katterle, K. R. Stand, A. Palmer, S.-K. Lee, E. I. Solomon, A. Gräslund,
A.-L. Barra Examples of High Frequency EPR Studies in Bioinorganic Chemistry. J. Biol. Inorg. Chem. 2003, 8;
235-247.
[5] K.R. Strand, S. Karlsen, K.K. Andersson. Cobalt substitution of mouse R2 ribonucleotide reductase as a
model for the reactive diferrous state. Spectroscopic and structural evidence for a ferromagnetically coupled
dinuclear cobalt cluster. J. Biol. Chem. 2002, 277; 34229-34238.
[6] K.R. Strand, S. Karlsen, S., M. Kolberg, Å.K. Røhr, C.H. Gørbitz, K. K. Andersson. Crystal Structural
Studies of Changes in the Native Dinuclear Iron Center of Ribonucleotide Reductase Protein R2 from Mouse J.
Biol. Chem. 2004, 279; 46794-46801
[7] Wei P.P, Tomter A.B, Røhr, Å.K. Andersson K.K., Solomon, E.I. Circular dichroism and magnetic circular
dichroism studies of the active site of p53R2 from human and mouse: iron binding and nature of the biferrous
site relative to other ribonucleotide reductases. Biochemistry, 2006, 45; 14043-14051
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