1pm2
|
CRYSTAL STRUCTURE OF MANGANESE SUBSTITUTED R2-D84E (D84E MUTANT OF THE R2 SUBUNIT OF E. COLI RIBONUCLEOTIDE REDUCTASE)
OverviewOverview
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.
About this StructureAbout this Structure
1PM2 is a Single protein structure of sequence from Escherichia coli with MN and HG as ligands. Active as Ribonucleoside-diphosphate reductase, with EC number 1.17.4.1 Full crystallographic information is available from OCA.
ReferenceReference
Variable coordination geometries at the diiron(II) active site of ribonucleotide reductase R2., Voegtli WC, Sommerhalter M, Saleh L, Baldwin J, Bollinger JM Jr, Rosenzweig AC, J Am Chem Soc. 2003 Dec 24;125(51):15822-30. PMID:14677973
Page seeded by OCA on Tue Nov 20 23:55:01 2007