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1.
Proc Natl Acad Sci U S A ; 119(31): e2122677119, 2022 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-35881795

RESUMO

Synthetic iron-sulfur cubanes are models for biological cofactors, which are essential to delineate oxidation states in the more complex enzymatic systems. However, a complete series of [Fe4S4]n complexes spanning all redox states accessible by 1-electron transformations of the individual iron atoms (n = 0-4+) has never been prepared, deterring the methodical comparison of structure and spectroscopic signature. Here, we demonstrate that the use of a bulky arylthiolate ligand promoting the encapsulation of alkali-metal cations in the vicinity of the cubane enables the synthesis of such a series. Characterization by EPR, 57Fe Mössbauer spectroscopy, UV-visible electronic absorption, variable-temperature X-ray diffraction analysis, and cyclic voltammetry reveals key trends for the geometry of the Fe4S4 core as well as for the Mössbauer isomer shift, which both correlate systematically with oxidation state. Furthermore, we confirm the S = 4 electronic ground state of the most reduced member of the series, [Fe4S4]0, and provide electrochemical evidence that it is accessible within 0.82 V from the [Fe4S4]2+ state, highlighting its relevance as a mimic of the nitrogenase iron protein cluster.


Assuntos
Materiais Biomiméticos , Coenzimas , Hidrocarbonetos , Ferro , Nitrogenase , Enxofre , Materiais Biomiméticos/síntese química , Materiais Biomiméticos/química , Coenzimas/síntese química , Coenzimas/química , Hidrocarbonetos/síntese química , Hidrocarbonetos/química , Ferro/química , Nitrogenase/química , Oxirredução , Enxofre/química
2.
J Am Chem Soc ; 146(10): 6493-6505, 2024 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-38426440

RESUMO

PylB is a radical S-adenosyl-l-methionine (SAM) enzyme predicted to convert l-lysine into (3R)-3-methyl-d-ornithine, a precursor in the biosynthesis of the 22nd proteogenic amino acid pyrrolysine. This protein highly resembles that of the radical SAM tyrosine and tryptophan lyases, which activate their substrate by abstracting a H atom from the amino-nitrogen position. Here, combining in vitro assays, analytical methods, electron paramagnetic resonance spectroscopy, and theoretical methods, we demonstrated that instead, PylB activates its substrate by abstracting a H atom from the Cγ position of l-lysine to afford the radical-based ß-scission. Strikingly, we also showed that PylB catalyzes the reverse reaction, converting (3R)-3-methyl-d-ornithine into l-lysine and using catalytic amounts of the 5'-deoxyadenosyl radical. Finally, we identified significant in vitro production of 5'-thioadenosine, an unexpected shunt product that we propose to result from the quenching of the 5'-deoxyadenosyl radical species by the nearby [Fe4S4] cluster.


Assuntos
Metionina , Ornitina/análogos & derivados , S-Adenosilmetionina , S-Adenosilmetionina/metabolismo , Lisina , Racemetionina , Espectroscopia de Ressonância de Spin Eletrônica
3.
Inorg Chem ; 63(19): 8730-8738, 2024 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-38687645

RESUMO

Iron-sulfur (Fe-S) clusters are essential inorganic cofactors dedicated to a wide range of biological functions, including electron transfer and catalysis. Specialized multiprotein machineries present in all types of organisms support their biosynthesis. These machineries encompass a scaffold protein, on which Fe-S clusters are assembled before being transferred to cellular targets. Here, we describe the first characterization of the native Fe-S cluster of the anaerobically purified SufBC2D scaffold from Escherichia coli by XAS and Mössbauer, UV-visible absorption, and EPR spectroscopies. Interestingly, we propose that SufBC2D harbors two iron-sulfur-containing species, a [2Fe-2S] cluster and an as-yet unidentified species. Mutagenesis and biochemistry were used to propose amino acid ligands for the [2Fe-2S] cluster, supporting the hypothesis that both SufB and SufD are involved in the Fe-S cluster ligation. The [2Fe-2S] cluster can be transferred to ferredoxin in agreement with the SufBC2D scaffold function. These results are discussed in the context of Fe-S cluster biogenesis.


Assuntos
Proteínas de Escherichia coli , Escherichia coli , Proteínas Ferro-Enxofre , Proteínas Ferro-Enxofre/química , Proteínas Ferro-Enxofre/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Espectroscopia de Mossbauer , Espectroscopia por Absorção de Raios X , Proteínas de Transporte
4.
Chemistry ; 28(70): e202201875, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36129399

RESUMO

Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor.


Assuntos
Compostos Férricos , Ferro , Compostos Férricos/química , Modelos Moleculares , Catálise , Ferro/química , Compostos Ferrosos/química
5.
Phys Rev Lett ; 125(26): 267204, 2020 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-33449788

RESUMO

Large spin Hall angles have been observed in 3d ferromagnets, but their origin, and especially their link with the ferromagnetic order, remain unclear. Here, we investigate the evolution of the inverse spin Hall effect of Ni_{60}Cu_{40} and Ni_{50}Cu_{50} across their Curie temperatures using spin-pumping experiments. We show that the inverse spin Hall effect in these samples is comparable to that of platinum, and that it is insensitive to the magnetic order. These results point toward a Heisenberg localized model of the transition and suggest that the large spin Hall effects in 3d ferromagnets can be independent of the magnetic phase.

6.
Chemistry ; 25(61): 13911-13920, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31334889

RESUMO

Molecular photosensitizers that are able to store multiple reducing equivalents are of great interest in the field of solar fuel production, where most reactions involve multielectronic reduction processes. In order to increase the reducing power of a ruthenium tris-diimine charge-photoaccumulating complex, two structural modifications on its fused dipyridophenazine-pyridoquinolinone ligand were computationally investigated. Addition of an electron-donating oxime group was calculated to substantially decrease the reduction potentials of the complex, thus guiding the synthesis of a pyridoquinolinone-oxime derivative. Its spectroscopic and (spectro)electrochemical characterization experimentally confirmed the DFT predictions, with the first and second reduction processes cathodically shifted by -0.24 and -0.14 V, respectively, compared to the parent complex. Moreover, the ability of this novel artificial photosynthetic system to store two photogenerated electrons at a more reducing potential, via a proton-coupled electron-transfer mechanism, was demonstrated.

7.
J Am Chem Soc ; 140(48): 16661-16668, 2018 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-30418774

RESUMO

The radical S-adenosyl-l-methionine tryptophan lyase uses radical-based chemistry to convert l-tryptophan into 3-methyl-2-indolic acid, a fragment in the biosynthesis of the thiopeptide antibiotic nosiheptide. This complex reaction involves several successive steps corresponding to (i) the activation by a specific hydrogen-atom abstraction, (ii) an unprecedented •CO2- radical migration, (iii) a cyanide fragment release, and (iv) the termination of the radical-based reaction. In vitro study of this reaction is made more difficult because the enzyme produces a significant amount of a shunt product instead of the natural product. Here, using a combination of X-ray crystallography, electron paramagnetic resonance spectroscopy, and quantum and hybrid quantum mechanical/molecular mechanical calculations, we have deciphered the fine mechanism of the key •CO2- radical migration, highlighting how the preorganized active site of the protein tightly controls this reaction.


Assuntos
Proteínas de Bactérias/metabolismo , Carbono-Carbono Liases/metabolismo , Triptofano/metabolismo , Proteínas de Bactérias/química , Carbono-Carbono Liases/química , Domínio Catalítico , Cristalografia por Raios X , Descarboxilação , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Modelos Moleculares , Ligação Proteica , Teoria Quântica , Streptomyces/enzimologia , Triptofano/química
8.
J Am Chem Soc ; 139(25): 8628-8638, 2017 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-28613072

RESUMO

We have investigated the influence of bound cations on the reduction of cobalt complexes of redox active ligands and explored the reactivity of reduced species with CO2. The one electron reduction of [CoII(Rsalophen)] with alkali metals (M = Li, Na, K) leads to either ligand-centered or metal-centered reduction depending on the alkali ion. It affords either the [CoI(Rsalophen)K] complexes or the [CoII2(bis-salophen)M2] (M = Li, Na) dimers that are present in solution in equilibrium with the respective [CoI(salophen)M] complexes. The two electron reduction of [CoII(OMesalophen)] results in both ligand centered and metal centered reduction affording the Co(I)-Co(II)-Co(I) [Co3(tris-OMesalophen)Na6(THF)6], 6 complex supported by a bridging deca-anionic tris-OMesalophen10- ligand where three OMesalophen units are connected by two C-C bonds. Removal of the Na ion from 6 leads to a redistribution of the electrons affording the complex [(Co(OMesalophen))2Na][Na(cryptand)]3, 7. The EPR spectrum of 7 suggests the presence of a Co(I) bound to a radical anionic ligand. Dissolution of 7 in pyridine leads to the isolation of [CoI2(bis-OMesalophen)Na2Py4][Na(cryptand)]2, 8. Complex 6 reacts with ambient CO2 leading to multiple CO2 reduction products. The product of CO2 addition to the OMesalophen ligand, [Co(OMesalophen-CO2)Na]2[Na(cryptand)]2, 9, was isolated but CO32- formation in 53% yield was also detected. Thus, the electrons stored in the reversible C-C bonds may be used for the transformation of carbon dioxide.

9.
Angew Chem Int Ed Engl ; 56(45): 13995-13998, 2017 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-28892584

RESUMO

Yttrium aluminum borate (YAB) powders prepared by sol-gel process have been investigated to understand their photoluminescence (PL) mechanism. The amorphous YAB powders exhibit bright visible PL from blue emission for powders calcined at 450 °C to broad white PL for higher calcination temperature. Thanks to 13 C labelling, NMR and EPR studies show that propionic acid initially used to solubilize the yttrium nitrate is decomposed into aromatic molecules confined within the inorganic matrix. DTA-TG-MS analyses show around 2 wt % of carbogenic species. The PL broadening corresponds to the apparition of a new band at 550 nm, associated with the formation of aromatic species. Furthermore, pulsed ENDOR spectroscopy combined with DFT calculations enables us to ascribe EPR spectra to free radicals derived from small (2 to 3 rings) polycyclic aromatic hydrocarbons (PAH). PAH molecules are thus at the origin of the PL as corroborated by slow afterglow decay and thermoluminescence experiments.

10.
Biochemistry ; 55(41): 5798-5808, 2016 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-27677419

RESUMO

RimO, a radical-S-adenosylmethionine (SAM) enzyme, catalyzes the specific C3 methylthiolation of the D89 residue in the ribosomal S12 protein. Two intact iron-sulfur clusters and two SAM cofactors both are required for catalysis. By using electron paramagnetic resonance, Mössbauer spectroscopies, and site-directed mutagenesis, we show how two SAM molecules sequentially bind to the unique iron site of the radical-SAM cluster for two distinct chemical reactions in RimO. Our data establish that the two SAM molecules bind the radical-SAM cluster to the unique iron site, and spectroscopic evidence obtained under strongly reducing conditions supports a mechanism in which the first molecule of SAM causes the reoxidation of the reduced radical-SAM cluster, impeding reductive cleavage of SAM to occur and allowing SAM to methylate a HS- ligand bound to the additional cluster. Furthermore, by using density functional theory-based methods, we provide a description of the reaction mechanism that predicts the attack of the carbon radical substrate on the methylthio group attached to the additional [4Fe-4S] cluster.


Assuntos
Proteínas Ferro-Enxofre/metabolismo , S-Adenosilmetionina/metabolismo , Sulfurtransferases/metabolismo , Catálise , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Mutagênese Sítio-Dirigida , Oxirredução , Análise Espectral/métodos , Sulfurtransferases/genética
11.
J Biol Inorg Chem ; 21(4): 549-57, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27259294

RESUMO

Radical SAM enzymes generally contain a [4Fe-4S](2+/1+) (RS cluster) cluster bound to the protein via the three cysteines of a canonical motif CxxxCxxC. The non-cysteinyl iron is used to coordinate SAM via its amino-carboxylate moiety. The coordination-induced proximity between the cluster acting as an electron donor and the adenosyl-sulfonium bond of SAM allows for the homolytic cleavage of the latter leading to the formation of the reactive 5'-deoxyadenosyl radical used for substrate activation. Most of the structures of Radical SAM enzymes have been obtained in the presence of SAM, and therefore, little is known about the situation when SAM is not present. In this report, we show that RimO, a methylthiotransferase belonging to the radical SAM superfamily, binds a Tris molecule in the absence of SAM leading to specific spectroscopic signatures both in Mössbauer and pulsed EPR spectroscopies. These data provide a cautionary note for researchers who work with coordinative unsaturated iron sulfur clusters.


Assuntos
S-Adenosilmetionina/química , Sulfurtransferases/química , Trometamina/química , Soluções Tampão , S-Adenosilmetionina/metabolismo , Sulfurtransferases/metabolismo , Thermotoga maritima/enzimologia
12.
Nat Chem Biol ; 9(5): 333-8, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23542644

RESUMO

How living organisms create carbon-sulfur bonds during the biosynthesis of critical sulfur-containing compounds is still poorly understood. The methylthiotransferases MiaB and RimO catalyze sulfur insertion into tRNAs and ribosomal protein S12, respectively. Both belong to a subgroup of radical-S-adenosylmethionine (radical-SAM) enzymes that bear two [4Fe-4S] clusters. One cluster binds S-adenosylmethionine and generates an Ado• radical via a well-established mechanism. However, the precise role of the second cluster is unclear. For some sulfur-inserting radical-SAM enzymes, this cluster has been proposed to act as a sacrificial source of sulfur for the reaction. In this paper, we report parallel enzymological, spectroscopic and crystallographic investigations of RimO and MiaB, which provide what is to our knowledge the first evidence that these enzymes are true catalysts and support a new sulfation mechanism involving activation of an exogenous sulfur cosubstrate at an exchangeable coordination site on the second cluster, which remains intact during the reaction.


Assuntos
Proteínas Ferro-Enxofre/química , Proteínas Ferro-Enxofre/metabolismo , S-Adenosilmetionina/metabolismo , Enxofre/metabolismo , Sulfurtransferases/metabolismo , Thermotoga maritima/metabolismo , Biocatálise , Cristalografia por Raios X , Radicais Livres/metabolismo , Modelos Moleculares , Estrutura Molecular , Enxofre/química , Sulfurtransferases/química , Thermotoga maritima/enzimologia
13.
J Am Chem Soc ; 136(18): 6716-23, 2014 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-24712893

RESUMO

The metal-mediated redox transformation of CO2 in mild conditions is an area of great current interest. The role of cooperativity between a reduced metal center and a Lewis acid center in small-molecule activation is increasingly recognized, but has not so far been investigated for f-elements. Here we show that the presence of potassium at a U, K site supported by sterically demanding tris(tert-butoxy)siloxide ligands induces a large cooperative effect in the reduction of CO2. Specifically, the ion pair complex [K(18c6)][U(OSi(O(t)Bu)3)4], 1, promotes the selective reductive disproportionation of CO2 to yield CO and the mononuclear uranium(IV) carbonate complex [U(OSi(O(t)Bu)3)4(µ-κ(2):κ(1)-CO3)K2(18c6)], 4. In contrast, the heterobimetallic complex [U(OSi(O(t)Bu)3)4K], 2, promotes the potassium-assisted two-electron reductive cleavage of CO2, yielding CO and the U(V) terminal oxo complex [UO(OSi(O(t)Bu)3)4K], 3, thus providing a remarkable example of two-electron transfer in U(III) chemistry. DFT studies support the presence of a cooperative effect of the two metal centers in the transformation of CO2.

14.
J Biol Inorg Chem ; 19(1): 75-84, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24240692

RESUMO

The biosynthesis of the organometallic H cluster of [Fe-Fe] hydrogenase requires three accessory proteins, two of which (HydE and HydG) belong to the radical S-adenosylmethionine enzyme superfamily. The third, HydF, is an Fe-S protein with GTPase activity. The [4Fe-4S] cluster of HydF is bound to the polypeptide chain through only the three, conserved, cysteine residues present in the binding sequence motif CysXHisX(46-53)HisCysXXCys. However, the involvement of the two highly conserved histidines as a fourth ligand for the cluster coordination is controversial. In this study, we set out to characterize further the [4Fe-4S] cluster of HydF using Mössbauer, EPR, hyperfine sublevel correlation (HYSCORE), and resonance Raman spectroscopy in order to investigate the influence of nitrogen ligands on the spectroscopic properties of [4Fe-4S](2+/+) clusters. Our results show that Mössbauer, resonance Raman, and EPR spectroscopy are not able to readily discriminate between the imidazole-coordinated [4Fe-4S] cluster and the non-imidazole-bound [4Fe-4S] cluster with an exchangeable fourth ligand that is present in wild-type HydF. HYSCORE spectroscopy, on the other hand, detects the presence of an imidazole/histidine ligand on the cluster on the basis of the appearance of a specific spectral pattern in the strongly coupled region, with a coupling constant of approximately 6 MHz. We also discovered that a His-tagged version of HydF, with a hexahistidine tag at the N-terminus, has a [4Fe-4S] cluster coordinated by one histidine from the tag. This observation strongly indicates that care has to be taken in the analysis of data obtained on tagged forms of metalloproteins.


Assuntos
Proteínas Ferro-Enxofre/química , Thermotoga maritima/enzimologia , Espectroscopia de Ressonância de Spin Eletrônica , Histidina/química , Hidrogenase/metabolismo , Proteínas Ferro-Enxofre/metabolismo , Espectroscopia de Mossbauer , Análise Espectral Raman , Thermotoga maritima/química , Thermotoga maritima/metabolismo
15.
Adv Mater ; 36(14): e2304243, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38160244

RESUMO

2D materials, such as transition metal dichalcogenides, are ideal platforms for spin-to-charge conversion (SCC) as they possess strong spin-orbit coupling (SOC), reduced dimensionality and crystal symmetries as well as tuneable band structure, compared to metallic structures. Moreover, SCC can be tuned with the number of layers, electric field, or strain. Here, SCC in epitaxially grown 2D PtSe2 by THz spintronic emission is studied since its 1T crystal symmetry and strong SOC favor SCC. High quality of as-grown PtSe2 layers is demonstrated, followed by in situ ferromagnet deposition by sputtering that leaves the PtSe2 unaffected, resulting in well-defined clean interfaces as evidenced with extensive characterization. Through this atomic growth control and using THz spintronic emission, the unique thickness-dependent electronic structure of PtSe2 allows the control of SCC. Indeed, the transition from the inverse Rashba-Edelstein effect (IREE) in 1-3 monolayers (ML) to the inverse spin Hall effect (ISHE) in multilayers (>3 ML) of PtSe2 enabling the extraction of the perpendicular spin diffusion length and relative strength of IREE and ISHE is demonstrated. This band structure flexibility makes PtSe2 an ideal candidate to explore the underlying mechanisms and engineering of the SCC as well as for the development of tuneable THz spintronic emitters.

16.
J Biol Chem ; 287(49): 41174-85, 2012 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-23043105

RESUMO

Wybutosine and its derivatives are found in position 37 of tRNA encoding Phe in eukaryotes and archaea. They are believed to play a key role in the decoding function of the ribosome. The second step in the biosynthesis of wybutosine is catalyzed by TYW1 protein, which is a member of the well established class of metalloenzymes called "Radical-SAM." These enzymes use a [4Fe-4S] cluster, chelated by three cysteines in a CX(3)CX(2)C motif, and S-adenosyl-L-methionine (SAM) to generate a 5'-deoxyadenosyl radical that initiates various chemically challenging reactions. Sequence analysis of TYW1 proteins revealed, in the N-terminal half of the enzyme beside the Radical-SAM cysteine triad, an additional highly conserved cysteine motif. In this study we show by combining analytical and spectroscopic methods including UV-visible absorption, Mössbauer, EPR, and HYSCORE spectroscopies that these additional cysteines are involved in the coordination of a second [4Fe-4S] cluster displaying a free coordination site that interacts with pyruvate, the second substrate of the reaction. The presence of two distinct iron-sulfur clusters on TYW1 is reminiscent of MiaB, another tRNA-modifying metalloenzyme whose active form was shown to bind two iron-sulfur clusters. A possible role for the second [4Fe-4S] cluster in the enzyme activity is discussed.


Assuntos
Proteínas Arqueais/química , Proteínas Arqueais/genética , Carboxiliases/fisiologia , Oxirredutases/fisiologia , Pyrococcus abyssi/enzimologia , Proteínas de Saccharomyces cerevisiae/fisiologia , Sequência de Aminoácidos , Proteínas Arqueais/fisiologia , Carboxiliases/genética , Catálise , Cromatografia Líquida de Alta Pressão , Clonagem Molecular , Análise por Conglomerados , Cisteína/genética , Espectroscopia de Ressonância de Spin Eletrônica , Guanosina/análogos & derivados , Guanosina/química , Proteínas Ferro-Enxofre/química , Espectrometria de Massas/métodos , Modelos Químicos , Dados de Sequência Molecular , Oxirredutases/genética , Pyrococcus abyssi/genética , Ácido Pirúvico/química , RNA de Transferência/metabolismo , S-Adenosilmetionina/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Homologia de Sequência de Aminoácidos , Especificidade por Substrato , Raios Ultravioleta
17.
J Am Chem Soc ; 135(2): 733-40, 2013 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-23265191

RESUMO

Iron-sulfur (Fe-S) cluster-containing proteins are essential components of cells. In eukaryotes, Fe-S clusters are synthesized by the mitochondrial iron-sulfur cluster (ISC) machinery and the cytosolic iron-sulfur assembly (CIA) system. In the mammalian ISC machinery, preassembly of the Fe-S cluster on the scaffold protein (ISCU) involves a cysteine desulfurase complex (NFS1/ISD11) and frataxin (FXN), the protein deficient in Friedreich's ataxia. Here, by comparing the biochemical and spectroscopic properties of quaternary (ISCU/NFS1/ISD11/FXN) and ternary (ISCU/NFS1/ISD11) complexes, we show that FXN stabilizes the quaternary complex and controls iron entry to the complex through activation of cysteine desulfurization. Furthermore, we show for the first time that in the presence of iron and L-cysteine, an [Fe(4)S(4)] cluster is formed within the quaternary complex that can be transferred to mammalian aconitase (mACO2) to generate an active enzyme. In the absence of FXN, although the ternary complex can assemble an Fe-S cluster, the cluster is inefficiently transferred to ACO2. Taken together, these data help to unravel further the Fe-S cluster assembly process and the molecular basis of Friedreich's ataxia.


Assuntos
Proteínas de Ligação ao Ferro/fisiologia , Proteínas Ferro-Enxofre/química , Ferro/metabolismo , Enxofre/metabolismo , Animais , Complexos de Coordenação/química , Humanos , Modelos Moleculares , Frataxina
18.
J Phys Chem Lett ; 14(44): 10032-10038, 2023 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-37906734

RESUMO

Since the introduction of DNA-based architectures, in the past decade, DNA tetrahedrons have aroused great interest. Applications of such nanostructures require structural control, especially in the perspective of their possible functionalities. In this work, an integrated approach for structural characterization of a tetrahedron structure is proposed with a focus on the fundamental biophysical aspects driving the assembly process. To address such an issue, spin-labeled DNA sequences are chemically synthesized, self-assembled, and then analyzed by Continuous-Wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) spectroscopy. Interspin distance measurements based on PELDOR/DEER techniques combined with molecular dynamics (MD) thus revealed unexpected dynamic heterogeneity and flexibility of the assembled structures. The observation of flexibility in these ordered 3D structures demonstrates the sensitivity of this approach and its effectiveness in accessing the main dynamic and structural features with unprecedented resolution.


Assuntos
DNA , Simulação de Dinâmica Molecular , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Marcadores de Spin , DNA/química , Sequência de Bases
19.
Phys Chem Chem Phys ; 14(4): 1399-407, 2012 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-22146900

RESUMO

Magnetic properties of a doped linear polyarylamine (PA2), whose chain includes alternating para-phenylene and meta-phenylene groups, and of two cyclic and linear model compounds (C2 and D2) were explored by pulsed-EPR nutation spectroscopy, SQUID magnetometry and DFT calculations. Stoichiometrically doped PA2 samples exhibit a pure S = 1 state (exchange coupling constant J = 18 K) with a high spin concentration (0.65) corresponding to 65% of mers bearing holes. Such properties were already observed for doped reticulated polyarylamines but are quite unusual for doped linear polyarylamines. In order to better understand the properties of PA2, model compounds C2 and D2 were also investigated: pure S = 1 spin states could also be obtained, but with higher J (respectively 57 K and 35 K) and, surprisingly, with high but still limited spin concentrations (respectively 0.77 and 0.65).

20.
Chembiochem ; 12(17): 2560-3, 2011 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-21984076

RESUMO

In a spin: Spin-labeled oligonucleotides produced by click chemistry can be studied by EPR, by using a DEER sequence. This was used to test a complex triple-labeling strategy with damaged DNA. Extensive and accurate analysis of DNA structure and enzymatic repair processes were performed after digestion by EndoIV. Modified DNA structures and DNA-protein interactions can now be readily studied.


Assuntos
DNA/metabolismo , Desoxirribonuclease IV (Fago T4-Induzido)/metabolismo , Marcadores de Spin , Química Click , Clivagem do DNA , Dano ao DNA , Espectroscopia de Ressonância de Spin Eletrônica , Oligonucleotídeos/química
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