1PIY

RIBONUCLEOTIDE REDUCTASE R2 SOAKED WITH FERROUS ION AT NEUTRAL PH

Summary for 1PIY

• Entry DOI: 10.2210/pdb1piy/pdb
• Related: 1PIM 1PIU 1PIZ 1PJ0 1PJ1
• Descriptor: Ribonucleoside-diphosphate reductase 1 beta chain, FE (III) ION, MERCURY (II) ION, ... (4 entities in total)
• Functional Keywords: four-helix bundle, diferrous cluster, oxidoreductase
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 89857.31

Authors

Voegtli, W.C.,Sommerhalter, M.,Saleh, L.,Baldwin, J.,Bollinger Jr., J.M.,Rosenzweig, A.C. (deposition date: 2003-05-30, release date: 2004-01-13, Last modification date: 2023-08-16)

Primary citation

Voegtli, W.C.,Sommerhalter, M.,Saleh, L.,Baldwin, J.,Bollinger Jr., J.M.,Rosenzweig, A.C.
Variable coordination geometries at the diiron(II) active site of ribonucleotide reductase R2.
J.Am.Chem.Soc., 125:15822-15830, 2003

PubMed Abstract: The R2 subunit of Escherichia coli ribonucleotide reductase contains a dinuclear iron center that generates a catalytically essential stable tyrosyl radical by one electron oxidation of a nearby tyrosine residue. After acquisition of Fe(II) ions by the apo protein, the resulting diiron(II) center reacts with O(2) to initiate formation of the radical. Knowledge of the structure of the reactant diiron(II) form of R2 is a prerequisite for a detailed understanding of the O(2) activation mechanism. Whereas kinetic and spectroscopic studies of the reaction have generally been conducted at pH 7.6 with reactant produced by the addition of Fe(II) ions to the apo protein, the available crystal structures of diferrous R2 have been obtained by chemical or photoreduction of the oxidized diiron(III) protein at pH 5-6. To address this discrepancy, we have generated the diiron(II) states of wildtype R2 (R2-wt), R2-D84E, and R2-D84E/W48F by infusion of Fe(II) ions into crystals of the apo proteins at neutral pH. The structures of diferrous R2-wt and R2-D48E determined from these crystals reveal diiron(II) centers with active site geometries that differ significantly from those observed in either chemically or photoreduced crystals. Structures of R2-wt and R2-D48E/W48F determined at both neutral and low pH are very similar, suggesting that the differences are not due solely to pH effects. The structures of these "ferrous soaked" forms are more consistent with circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopic data and provide alternate starting points for consideration of possible O(2) activation mechanisms.

PubMed: 14677973
DOI: 10.1021/ja0370387

Experimental method

X-RAY DIFFRACTION (1.68 Å)