Spectroscopic and Redox Studies of Valence-Delocalized [Fe2S2]+ Centers in Thioredoxin-like Ferredoxins

Subramanian, Sowmya; Duin, Evert C.; Fawcett, Sarah E. J.; Armstrong, Fräser A.; Meyer, Jacques; Johnson, Michael K.

doi:10.1021/jacs.5b01869

Cited by 21 publications

(18 citation statements)

References 40 publications

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“…Compared with species I, which undergoes no significant broadening at 70 K, species II is faster relaxing and is significantly broadened above 50 K. These resonances show increased g-value anisotropy and decreased g av values compared with the all-cysteine-ligated [Fe 2 S 2 ] 1ϩ centers. However, similar EPR spectra have been observed for Cys-to-Ser variants at the reducible site of all-cysteine-ligated [Fe 2 S 2 ] 1ϩ centers in ferredoxins (45)(46)(47)(48)(49) and of [Fe 2 S 2 ] 1ϩ centers with one or two His ligands at the reducible site (50 -54).…”

Section: Plant Dihydroxyacid Dehydratase [Fe 2 S 2 ] Centersupporting

confidence: 65%

Function and maturation of the Fe–S center in dihydroxyacid dehydratase from Arabidopsis

Gao

Azam

Randeniya

et al. 2018

Journal of Biological Chemistry

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Dihydroxyacid dehydratase (DHAD) is the third enzyme required for branched-chain amino acid biosynthesis in bacteria, fungi, and plants. DHAD enzymes contain two distinct types of active-site Fe-S clusters. The best characterized examples are DHAD, which contains an oxygen-labile [FeS] cluster, and spinach DHAD, which contains an oxygen-resistant [FeS] cluster. Although the Fe-S cluster is crucial for DHAD function, little is known about the cluster-coordination environment or the mechanism of catalysis and cluster biogenesis. Here, using the combination of UV-visible absorption and circular dichroism and resonance Raman and electron paramagnetic resonance, we spectroscopically characterized the Fe-S center in DHAD from (). Our results indicated that DHAD can accommodate [FeS] and [FeS] clusters. However, only the [FeS] cluster-bound form is catalytically active. We found that the [FeS] cluster is coordinated by at least one non-cysteinyl ligand, which can be replaced by the thiol group(s) of dithiothreitol. cluster transfer and reconstitution reactions revealed that [FeS] cluster-containing NFU2 protein is likely the physiological cluster donor for maturation ofDHAD. In summary, DHAD binds either one [FeS] or one [FeS] cluster, with only the latter being catalytically competent and capable of substrate and product binding, and NFU2 appears to be the physiological [FeS] cluster donor for DHAD maturation. This work represents the first characterization of recombinantDHAD, providing new insights into the properties, biogenesis, and catalytic role of the active-site Fe-S center in a plant DHAD.

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Section: Plant Dihydroxyacid Dehydratase [Fe 2 S 2 ] Centersupporting

confidence: 65%

Function and maturation of the Fe–S center in dihydroxyacid dehydratase from Arabidopsis

Gao

Azam

Randeniya

et al. 2018

Journal of Biological Chemistry

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“…In these cases of very large | B / J |, modestly large vibronic couplings, such as that observed in the [Fe 2 (OH) 3 ] 3+ complex 5 , still do not overcome the Heisenberg double-exchange interaction, resulting in a single-well S = 9/2 ground spin state with complete electron delocalization (Fig. 1d ), These few examples demonstrate that under certain conditions the localizing effects of vibronic coupling and other trapping forces can be surmounted 4 , 5 , 25 , further suggesting that intermediate spin states may be achievable within the vibronic coupling-extended formalism of Heisenberg double exchange (Fig. 1e ).…”

Section: Mainmentioning

confidence: 95%

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes

et al. 2022

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The electronic structure and ground spin states, S, observed for mixed-valent iron–sulfur dimers (FeII-FeIII) are typically determined by the Heisenberg exchange interaction, J, that couples the magnetic interaction of the two metal centres either ferromagnetically (J > 0, S = 9/2) or antiferromagnetically (J < 0, S = 1/2). In the case of antiferromagnetically coupled iron centres, stabilization of the high-spin S = 9/2 ground state is also feasible through a Heisenberg double-exchange interaction, B, which lifts the degeneracy of the Heisenberg spin states. This theorem also predicts intermediate spin states for mixed-valent dimers, but those have so far remained elusive. Herein, we describe the structural, electron paramagnetic resonance and Mössbauer spectroscopic, and magnetic characterization of a series of mixed-valent complexes featuring [Fe2Q2]+ (Q = S2–, Se2–, Te2–), where the Se and Te complexes favour S = 3/2 spin states. The incorporation of heavier chalcogenides in this series reveals a delicate balance of antiferromagnetic coupling, Heisenberg double-exchange and vibronic coupling.

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“…Due to the absence of PLP in Mm CobD K234A , we used the spectrum of this protein to try to identify the nature of the Fe chromophore present in the protein. The UV–vis absorption spectrum of the chromophore in Mm CobD K234A did not resemble that of rubredoxin [1Fe-0S] centers, which typically have λ max features at 370 and 492 nm. , Nor did it resemble the spectra of ferredoxin-type [2Fe-2S] cluster proteins, which have λ max features at 330, 422, and 464 nm, thioredoxin-like proteins, or other [2Fe-2S] cluster-containing proteins. − The Mm CobD WT spectrum features a broad band with a λ max at ∼420 nm, typical of [4Fe-4S] 2+ clusters. , …”

Section: Resultsmentioning

confidence: 98%

The l-Thr Kinase/l-Thr-Phosphate Decarboxylase (CobD) Enzyme from Methanosarcina mazei Gö1 Contains Metallocenters Needed for Optimal Activity

et al. 2019

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The MM2060 (cobD) gene from Methanosarcina mazei strain Gö1 encodes a protein (MmCobD) with L-threonine kinase (PduX) and L-threonine-O-3-phosphate decarboxylase (CobD) activities. In addition to the unexpected L-Thr kinase activity, MmCobD has an extended carboxy-terminal (C-terminal) region annotated as a putative metal-binding zinc finger-like domain. Here we demonstrate that the C-terminus of MmCobD is a ferroprotein containing ~25 non-heme iron atoms per monomer of protein. The absence of the C-terminus substantially reduces, but does not abolish, enzymatic activities in vitro and in vivo. Single residue substitutions of C-terminal putative Fe-binding cysteinyl and histidinyl residues resulted in the loss of Fe and changes in enzyme activity levels. Salmonella enterica ΔpduX or ΔcobD strains were used as heterologous hosts to assess coenzyme B 12 biosynthesis as a function of MmCobD variants. Some of the latter displayed 5-fold higher enzymatic activity in vitro, and enhanced the growth rate of the S. enterica strains that synthesized them. Most of the MmCobD variants tested were 2-to 6-fold less active in vitro, and supported slow growth rates of the S. enterica strains that synthesized them; some substitutions abolished enzyme activity. MmCobD exhibited an ultraviolet-visible absorption spectrum consistent with [4Fe-4S] clusters that appeared to be susceptible to oxidation by H 2 O 2 and reduction by sodium dithionite. The presence of FeS clusters in MmCobD was corroborated by electron paramagnetic resonance and magnetic circular dichroism studies. Collectively, our results suggest that MmCobD contains one or more diamagnetic [4Fe-4S] 2+ center(s) that may play a structural or regulatory role.

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Spectroscopic and Redox Studies of Valence-Delocalized [Fe₂S₂]⁺ Centers in Thioredoxin-like Ferredoxins

Cited by 21 publications

References 40 publications

Function and maturation of the Fe–S center in dihydroxyacid dehydratase from Arabidopsis

Function and maturation of the Fe–S center in dihydroxyacid dehydratase from Arabidopsis

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes

The l-Thr Kinase/l-Thr-Phosphate Decarboxylase (CobD) Enzyme from Methanosarcina mazei Gö1 Contains Metallocenters Needed for Optimal Activity

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