The Fe-only nitrogenase from Rhodobacter capsulatus: identification of the cofactor, an unusual, high-nuclearity iron-sulfur cluster, by Fe K-edge EXAFS and 57Fe Mössbauer spectroscopy

Krahn, Eugen; Weiss, B. J. R.; Kröckel, Monika; Groppe, Jay C.; Henkel, Gerald; Cramer, Sp; Trautwein, A. X.; Schneider, Klaus; Müller, Achim

doi:10.1007/s007750100263

Cited by 98 publications

(146 citation statements)

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“…The EXAFS-derived 8Fe model for the NifEN-bound FeMoco precursor is structurally homologous to the cluster proposed as the catalytic cofactor in the alternative iron-only nitrogenase (FeFeco) (9,10) and is a good match to both the EXAFS results from this protein (27) and theoretically calculated distances for FeFeco (30)(31)(32). ʈ In accordance with the observation of longer distances in the NifEN-bound precursor compared with MoFe protein-bound FeMoco, density functional theory calculations predict that FeFeco is less stable than its molybdenum-containing counterpart and therefore should have a larger cluster volume (32,33).…”

Section: Resultsmentioning

confidence: 60%

“…4). Since its initial observation in the EXAFS Fourier transform of isolated FeMoco, this peak has been regarded as a signature feature representative of the unique long-range order in the FeMoco structure (24,(26)(27)(28). The occurrence of this signature peak in the data for the NifEN-bound precursor together with the EXAFS-fit results imply that the precursor has the same long-range order found in FeMoco.…”

Section: Resultsmentioning

confidence: 92%

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Structural insights into a protein-bound iron-molybdenum cofactor precursor

Corbett

Fay

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

102

107

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The iron-molybdenum cofactor (FeMoco) of the nitrogenase MoFe protein is a highly complex metallocluster that provides the catalytically essential site for biological nitrogen fixation. FeMoco is assembled outside the MoFe protein in a stepwise process requiring several components, including NifB-co, an iron-and sulfurcontaining FeMoco precursor, and NifEN, an intermediary assembly protein on which NifB-co is presumably converted to FeMoco. Through the comparison of Azotobacter vinelandii strains expressing the NifEN protein in the presence or absence of the nifB gene, the structure of a NifEN-bound FeMoco precursor has been analyzed by x-ray absorption spectroscopy. The results provide physical evidence to support a mechanism for FeMoco biosynthesis. The NifEN-bound precursor is found to be a molybdenum-free analog of FeMoco and not one of the more commonly suggested cluster types based on a standard [4Fe-4S] architecture. A facile scheme by which FeMoco and alternative, non-molybdenum-containing nitrogenase cofactors are constructed from this common precursor is presented that has important implications for the biosynthesis and biomimetic chemical synthesis of FeMoco.biosynthesis ͉ extended x-ray absorption fine structure ͉ nitrogenase ͉ x-ray absorption spectroscopy

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 92%

Structural insights into a protein-bound iron-molybdenum cofactor precursor

Corbett

Fay

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

102

107

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“…39 The structural analogy between the [Fe 8 S 7 ] core of 810 and the FeMo-cofactor raises a possibility that clusters 810 may be similar to the FeFe-cofactor of Fe-only nitrogenase, because the FeFe-cofactor has been suggested to be structurally similar to the FeMo-cofactor. 40 In the EPR spectrum of Feonly nitrogenase (FeFe protein) from Rhodobacter capsulatus, some states exhibit rhombic S = 1/2 signals at g = 1.96, 1.92, and 1.77 (turnover state) 41 and at g = 2.22, 2.05, 1.86 (pH 6.4, ¹5 mV vs. NHE, potential adjusted by the addition of hexacyanoferrate(III) as oxidant and Na 2 S 2 O 4 as reductant) possibly from the FeFe-cofactor, 42 and these signals happen to be similar to the EPR signals of 8 and 10.…”

Section: Award Accountsmentioning

confidence: 99%

Synthetic Analogues of the Active Sites of Nitrogenase and [NiFe] Hydrogenase

Ohki

2013

Bulletin of the Chemical Society of Japan

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Biological nitrogen fixation and H 2 metabolism are mediated by nitrogenase and hydrogenase, respectively. Their active sites consist of complex transition-metal sulfide/thiolate clusters, which have been long-standing synthetic challenges. This account describes our synthetic approaches toward the active sites of nitrogenase and [NiFe] hydrogenase. A new class of ironsulfur clusters modeling or structurally analogous to the nitrogenase metallo-clusters, namely P-cluster and FeMo-cofactor, have been synthesized from homogeneous self-assembly reactions of iron(II) amide or mesityl complexes with bulky thiols and elemental sulfur in toluene. A series of thiolate-bridged FeNi complexes modeling the active site of [NiFe] hydrogenase have been synthesized via two ways: One is to use iron(II)dithiolate complexes carrying CO and CN ligands as precursors to provide the (CO/CN)FeNi complexes. The other way is to split a tetranuclear (CO) 3 FeNiNiFe(CO) 3 complex, which is available from a sequential reaction of [FeBr 2 (CO) 4 ] with NaS t Bu and NiBr 2 (EtOH) 4 at ¹40°C.

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“…Moreover, they are consistent with the existence of Fe-only nitrogenases that appear to have a similar active site with Mo or V replaced by Fe. 254 Hence the role of the heterometal in the Mo and V nitrogenase active sites remains an enigma.…”

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confidence: 99%

Iron–Sulfur Proteins

Johnson

Smith

2005

Encyclopedia of Inorganic Chemistry

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Iron–sulfur proteins contain iron coordinated by at least one sulfur ligand and include proteins with mononuclear Fe centers with partial or complete cysteinyl sulfur ligation as well as proteins containing clusters of iron and inorganic sulfide. This review summarizes the structural, electronic, and redox properties of protein‐bound mononuclear FeS centers and FeS clusters containing [2Fe2S], [3Fe4S], and [4Fe4S] cores. In addition to the ubiquitous role in mediating biological electron transport, the roles of FeS centers have proliferated to include coupling of electron and proton transfer, substrate binding and activation, determining protein structure, regulation of gene expression and enzymatic activity, disulfide reduction, and iron, electron, or cluster storage. The diverse roles of FeS clusters are illustrated by discussion of specific systems: the mitochondrial and photosynthetic electron transport chains and a wide range of soluble redox enzymes and proteins; the active sites of nitrile hydratase, aconitase‐type (de)hydratases, superoxide reductase (SOR), radical‐SAM (S‐adenosylmethionine) enzymes, NiFe‐ and Fe‐hydrogenase, sulfite and nitrite reductase, nitrogenase, CO dehydrogenase, and acetyl‐CoA synthase; the structural FeS centers in DNA repair enzymes; the regulatory roles of FeS centers in the SoxR, fumarate–nitrate reduction (FNR), IscR/SufR, and iron‐regulatory protein (IRP) proteins and in selected enzymes; the two classes of FeS cluster containing disulfide reductases typified by ferredoxin–thioredoxin reductase (FTR) and heterodisulfide reductase (HDR); and the role of 8Fe ferredoxins and polyferredoxins in iron, electron, or cluster storage.

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The Fe-only nitrogenase from Rhodobacter capsulatus: identification of the cofactor, an unusual, high-nuclearity iron-sulfur cluster, by Fe K-edge EXAFS and 57Fe Mössbauer spectroscopy

Cited by 98 publications

References 0 publications

Structural insights into a protein-bound iron-molybdenum cofactor precursor

Structural insights into a protein-bound iron-molybdenum cofactor precursor

Synthetic Analogues of the Active Sites of Nitrogenase and [NiFe] Hydrogenase

Iron–Sulfur Proteins

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