Bridging-type changes facilitate successive oxidation steps at about 1V in two binuclear manganese complexes—implications for photosynthetic water-oxidation

Magnuson, Ann; Liebisch, Peter; Högblom, Joakim; Anderlund, Magnus F.; Lomoth, Reiner; Meyer‐Klaucke, Wolfram; Haumann, Michael; Dau, Holger

doi:10.1016/j.jinorgbio.2006.02.001

Cited by 50 publications

(43 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…4A) and XANES (Fig. 4B) of R2 ox and comparable Mn(II, III, IV) compounds (58,59). Indeed, the pre-edge spectrum of R2 ox was well reproduced by summation of the Mn(II, III, IV) spectra with relative weight- ings of 0.14, 0.62, and 0.24 (Fig.…”

Section: Electronic Features and Nuclear Geometry Of The Manganese Anmentioning

confidence: 75%

See 1 more Smart Citation

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Voevodskaya

Lendzian

Sanganas

et al. 2009

Journal of Biological Chemistry

View full text Add to dashboard Cite

The R2 protein of class I ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) can contain a Mn-Fe instead of the standard Fe-Fe cofactor. Ct R2 has a redox-inert phenylalanine replacing the radical-forming tyrosine of classic RNRs, which implies a different mechanism of O 2 activation. We studied the Mn-Fe site by x-ray absorption spectroscopy (XAS) and EPR. Reduced R2 in the R1R2 complex (R2 red ) showed an isotropic six-line EPR signal at g ϳ 2 of the Mn ( Ribonucleotide reductases (RNRs) 3 are the only enzymes that, in all organisms, catalyze the reduction of ribonucleotides to their deoxy forms essential for DNA synthesis (1-3). RNRs also are important targets in cancer and antiviral therapy (4, 5).Class I RNRs found in eukaryotes and microorganisms (6) are heterotetrameric enzymes of R1 2 R2 2 organization. The R1 protein contains the nucleotide binding site and R2 houses a dinuclear metal center, which is the site of dioxygen (O 2 ) activation and, in conventional RNRs, is of the Fe-Fe type (7).Extensive investigations on Fe-Fe RNRs from, e.g. Escherichia coli, Saccharomyces cerevisiae, Mus musculus, and Homo sapiens have established that the catalytic reactions involve activation of an O 2 molecule at the di-metal cluster to generate a high potential site, which oxidizes a nearby tyrosine residue to a tyrosyl radical, Y ⅐ (8 -10). In E. coli R2 this Tyr-122 is at ϳ6 Å distance to the nearest iron (11, 12). Subsequent proton-coupled electron transfer (13) leads to the re-reduction of Y ⅐ and to the oxidation of a cysteine at the substrate binding site in R1 to a radical (C ⅐ ) (14, 15). C ⅐ initiates ribonucleotide reduction involving disulfide formation by two additional cysteines (16). Regeneration of reduced cysteines requires electron input from external thio-or glutaredoxins and ultimately from NADPH (17).At least the Fe(II) 2 , Fe(III) 2 , Fe(IV)Fe(III), and Fe(IV) 2 oxidation states of the metal center seem to be involved in the electron transfer reactions (18, 19) of classic RNRs. The Fe(III)-Fe(IV) state, termed "intermediate X" (20,21), is crucial because it oxidizes the tyrosine to Y ⅐ , leaving the di-iron site in the Fe(III) 2 state. Y ⅐ usually survives a large number of catalytic cycles, but when it is lost, the inactive Fe(III) 2 -Met form remains (22). Reactivation of the enzyme first requires reduction of the metal site to Fe(II) 2 , which then must react with O 2 , leading to the cleavage of the O-O bond and again to the formation of Fe(III) 2 and Y ⅐ (22, 23).According to the above reaction sequences, a tyrosine radical and the Fe(IV)Fe(III) state (X) have been anticipated to be decisive for RNR function. This view has been challenged recently because R2 proteins of RNRs in several species have been discovered (24, 25), containing a redox-inert phenylalanine instead of the tyrosine. One enzyme is found in the important human pathogenic bacterium Chlamydia trachomatis (Ct) (25,26). It is a fully functional RNR and the only RNR encoded in the genome of this organism (27,28). ...

show abstract

Section: Electronic Features and Nuclear Geometry Of The Manganese Anmentioning

confidence: 75%

“…The small pre-edge magnitudes (Fig. 2) are explained by Mn(II/III) ions in near-octahedral geometries (39,57,58), but the flat edge maxima suggest marked Mn-ligand distance heterogeneity.…”

Section: Electronic Features and Nuclear Geometry Of The Manganese Anmentioning

confidence: 96%

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Voevodskaya

Lendzian

Sanganas

et al. 2009

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…The absolute E m values for the Mn(IV)Fe(III) states presumably are on the order of 1 V (30) and the slower XPR of the (III,III) states thus suggests a significant E m drop (104). A similar E m implies relatively minor structural differences between the FeFe and MnFe sites at least in the (III,III) states, as observed.…”

Section: Structures Of Fefe and Mnfe Cofactors-ourmentioning

confidence: 76%

Rapid X-ray Photoreduction of Dimetal-Oxygen Cofactors in Ribonucleotide Reductase

Sigfridsson

Chernev

Leidel

et al. 2013

Journal of Biological Chemistry

View full text Add to dashboard Cite

Background: Typical FeFe and MnFe cofactors bind to numerous enzymes such as ribonucleotide reductases. Crystallographic data suggest x-ray photoreduction (XPR) effects. Results: Rapid XPR-induced cofactor changes were monitored using time-resolved x-ray absorption spectroscopy. Conclusion: The XPR-induced cofactor states differ significantly from the native configurations, but comply with crystallographic structures. Significance: Structure determination for high-valent dimetal-oxygen cofactors requires free electron-laser protein crystallography combined with x-ray spectroscopy.

show abstract

“…[23] µ-Acetato/µ-hydroxo or µ-oxo bridging ligand changes in relation to Mn oxidation have been reported for synthetic binuclear Mn complexes with multidentate ancillary N and/ or O ligands. [24][25][26][27][28][29][30][31][32][33][34] Electrochemistry is a convenient way to investigate these kinds of redox-induced structural changes, and we have previously demonstrated the efficiency of the electrochemically induced core interconversion in an organic medium (CH 3 [35][36][37] have been structurally and spectroscopically characterized previously, and the electrochemical properties of 3 3+ have been briefly studied in CH 3 CN. [37,38] In contrast, complex 2 3+ , which possesses a rare mono-(µ-oxo) mono-(µ-acetato) motif, [39][40][41] has not been isolated previously and we report here its characterization by X-ray crystallography.…”

Section: Introductionmentioning

confidence: 99%

Redox‐Induced μ‐Acetato and μ‐Oxo Core Interconversions in Dinuclear Manganese Tris(2‐methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn₂^III(μ‐O)(μ‐O₂CCH₃)(tpa)₂]³⁺

et al. 2007

View full text Add to dashboard Cite

show abstract

Bridging-type changes facilitate successive oxidation steps at about 1V in two binuclear manganese complexes—implications for photosynthetic water-oxidation

Cited by 50 publications

References 64 publications

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Rapid X-ray Photoreduction of Dimetal-Oxygen Cofactors in Ribonucleotide Reductase

Redox‐Induced μ‐Acetato and μ‐Oxo Core Interconversions in Dinuclear Manganese Tris(2‐methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn₂^III(μ‐O)(μ‐O₂CCH₃)(tpa)₂]³⁺

Contact Info

Product

Resources

About

Bridging-type changes facilitate successive oxidation steps at about 1V in two binuclear manganese complexes—implications for photosynthetic water-oxidation

Cited by 50 publications

References 64 publications

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Redox Intermediates of the Mn-Fe Site in Subunit R2 of Chlamydia trachomatis Ribonucleotide Reductase

Rapid X-ray Photoreduction of Dimetal-Oxygen Cofactors in Ribonucleotide Reductase

Redox‐Induced μ‐Acetato and μ‐Oxo Core Interconversions in Dinuclear Manganese Tris(2‐methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn2III(μ‐O)(μ‐O2CCH3)(tpa)2]3+

Contact Info

Product

Resources

About

Redox‐Induced μ‐Acetato and μ‐Oxo Core Interconversions in Dinuclear Manganese Tris(2‐methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn₂^III(μ‐O)(μ‐O₂CCH₃)(tpa)₂]³⁺