Desulfoferrodoxin structure determined by MAD phasing and refinement to 1.9-Å resolution reveals a unique combination of a tetrahedral FeS4 centre with a square pyramidal FeSN4 centre

Coelho, Ana Varela; Matías, Pedro M.; Fulop,; Thompson, Andrew; González, Angeles Sánchez; Carrondo, Maria Arménia

doi:10.1007/s007750050184

Cited by 128 publications

(224 citation statements)

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“…Since the two iron centers exhibit very different structures and surroundings [11,14] The bi-molecular process associated with the data of Figure 5 suggests an intermolecular mechanism for electron transfer between center I of SOR and the center II of another SOR, as illustrated in Scheme 1. Indeed, our data gave no evidence of an intramolecular process between both iron centers.…”

Section: Discussionmentioning

confidence: 90%

“…The SOR active site is located at the surface of the protein and consists of a mononuclear iron center, named center II, pentacoordinated in its ferrous state by four nitrogen atoms from histidine residues in an equatorial plane and one sulfur atom from a cysteine residue in an axial position [11][12][13][14]. It displays a high redox potential of about + 300 mV (vs. NHE) at neutral pH and remains mainly in a reduced form in the presence of air [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…SORs having this additional iron center, e.g. the enzymes from Desulfovibrio desulfuricans [11], Desulfoarculus baarsii [5,14] and Desulfovibrio vulgaris [21], are named 2Fe-SOR whereas those having only the iron active site, like the enzymes from Pyrococcus furiosus [4,12], Archaeoglobus fulgidus [18] and Treponema pallidum [13] are named 1Fe-SORs.…”

Section: Introductionmentioning

confidence: 99%

“…Deletion of the iron center I in the D. vulgaris Hildenborough enzyme was shown to have no effect on the reactivity of the ferrous iron center II with superoxide [16]. It was proposed that center I could serve as an electronic relay between the cellular reductases and the catalytic iron site but the distance of 22 Å between iron center I and center II [11,14] was considered too long for efficient intramolecular electron transfer [28]. A well conserved tyrosine residue in 2Fe-SOR (Y115 in D. baarsii) located between center I and center II, at 10 Å from iron center II, was proposed to act as an electronic relay between the two iron centers ( Figure 1) [29], but up to now no studies have investigated these hypotheses.…”

Section: Introductionmentioning

confidence: 99%

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Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

et al. 2011

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Section: Discussionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

et al. 2011

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“…Both 1Fe and 2Fe SOR's have been characterized and found to have similar active site structures and reactivities. 8,9 The second Fe in the 2Fe SOR is in a rubredoxin-like Fe(SCys) 4 site for which the function is unknown as eliminating it by mutation does not affect the reactivity of this enzyme. 9…”

Section: Introductionmentioning

confidence: 99%

Sulfur K-Edge X-ray Absorption Spectroscopy and Density Functional Theory Calculations on Superoxide Reductase: Role of the Axial Thiolate in Reactivity

et al. 2007

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Superoxide reductase (SOR) is a non-heme iron enzyme which reduces superoxide to peroxide at a diffusion-controlled rate. Sulfur K-edge x-ray absorption spectroscopy (XAS) is used to investigate the ground state electronic structure of the resting high-spin and CN − bound low-spin Fe III forms of the 1Fe SOR from Pyrococcus furiosus. A computational model with constrained Imidazole rings (necessary for reproducing spin states), H-bonding interaction to the thiolate (necessary for reproducing Fe-S bond covalency of the high-spin and low-spin forms) and H-bonding to axial ligand (necessary to reproduce the ground state of the low-spin form) was developed and then used to investigate the enzymatic reaction mechanism. Reaction of the resting ferrous site with superoxide and protonation leading to a high-spin Fe III -OOH species and its subsequent protonation resulting in H 2 O 2 release is calculated to be the most energetically favorable reaction pathway. Our results suggest that the thiolate acts as a covalent anionic ligand. Replacing the thiolate with a neutral noncovalent ligand makes protonation very endothermic and greatly raises the reduction potential. The covalent nature of the thiolate weakens the Fe III bond to the proximal Oxygen of this hydroperoxo species, which raises its pK a by an additional 5 log units relative to a primarily anionic ligand facilitating its protonation. A comparison with Cytochrome P450 indicates that the stronger equatorial ligand field from the porphyrin results in a low-spin Fe III -OOH species which would not be capable of efficient H 2 O 2 release due to a spin-crossing barrier associated with formation of a high spin 5C Fe III product. Additionally, the presence of the di-anionic porphyrin π ring in Cytochrome P450 allows O-O heterolysis forming a Fe IV -oxo porphyrin radical species, which is calculated to be extremely unfavorable for the non-heme SOR ligand environment. Finally the 5C Fe III site which results from the product release at the end of the O 2 − reduction cycle is calculated to be capable of reacting with a second O 2 − resulting in superoxide dismutase (SOD) activity. However in contrast to FeSOD the 5C Fe III site of SOR which is more positive is calculated to have a high affinity for the binding a 6 th anionic ligand which would inhibit its SOD activity.

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Cytochrome c ₄

Andersen¹,

Christensen²,

Iversen³

et al. 2004

Handbook of Metalloproteins

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The di‐heme c ‐type cytochrome c 4 has been identified in the membrane space of a number of bacterial species, and the isolation and sequencing have been reported. The biological role is believed to be part of a respiratory chain. Recombinant cyt c 4 from Pseudomonas stutzeri (190 residues) has become available since the publication of the chapter. The 2.2 Å crystal structure has disclosed two almost equally sized globular domains, each with a His/Met axially coordinated heme group. Variable degrees of two‐fold structural symmetry can be distinguished. The relative heme group orientation is tilted with a short (2.6 Å) hydrogen bond between the propionate in each heme. The protein is strongly dipolar, with excess negative and positive charges of the N‐ and C‐terminal domains, respectively. UV/vis, nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and resonance Raman spectral data point to distinct electronic features of the heme groups. The oxidized N‐terminal heme is in a mixed high‐spin/low‐spin state, while the reduced N‐terminal heme and both oxidized and reduced C‐terminal heme are in a pure low‐spin state. Chemically induced sequential unfolding of the domains also reflects selective domain properties. As a two‐centre redox metalloprotein, cyt c 4 offers a prototype case for mechanistic mapping of a multi‐centre redox protein. Electron transfer between cyt c 4 and small reaction partners is multi‐phasic but the role of intramolecular electron transfer is inconclusive. Electrochemical electron transfer at low ionic strength, however, seems to involve unidirectional oxidation or reduction of the heme groups via intramolecular electron transfer. This may carry over to in vivo cyt c 4 function in membrane environments.

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Desulfoferrodoxin structure determined by MAD phasing and refinement to 1.9-Å resolution reveals a unique combination of a tetrahedral FeS4 centre with a square pyramidal FeSN4 centre

Cited by 128 publications

References 1 publication

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Sulfur K-Edge X-ray Absorption Spectroscopy and Density Functional Theory Calculations on Superoxide Reductase: Role of the Axial Thiolate in Reactivity

Cytochrome c ₄

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Desulfoferrodoxin structure determined by MAD phasing and refinement to 1.9-Å resolution reveals a unique combination of a tetrahedral FeS4 centre with a square pyramidal FeSN4 centre

Cited by 128 publications

References 1 publication

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Sulfur K-Edge X-ray Absorption Spectroscopy and Density Functional Theory Calculations on Superoxide Reductase: Role of the Axial Thiolate in Reactivity

Cytochrome c 4

Contact Info

Product

Resources

About

Cytochrome c ₄