All-Ferrous Titanium(III) Citrate Reduced Fe Protein of Nitrogenase:  An XAS Study of Electronic and Metrical Structure

Musgrave, Kristin B.; Angove, Hayley C.; Burgess, Barbara K.; Hedman, Britt; Hodgson, Keith O.

doi:10.1021/ja980598z

Cited by 86 publications

(118 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2) are consistent with spectroscopy on similar [Fe-S] cluster-containing proteins, displaying a 1s 3 3d pre-edge transition at ϳ7112 eV and a rising edge with a shoulder at ϳ7119 eV (37). Following treatment with IDS, the change to a higher oxidation state in the ⌬nifB MoFe protein is evident by a decrease in the intensity of the absorption edge at 7126 eV and by a 0.6-eV energy shift of the shoulder on the rising edge ( Fig.…”

Section: Resultssupporting

confidence: 85%

“…Because the edge represents the average iron site in an eight iron center, large shifts in energy are not expected. A 0.6-eV energy shift due to a two-electron oxidation, or an average change of 0.25 electrons/iron, is consistent with the shifts of 0.4 -0.5 eV seen for one-electron oxidations of the [Fe 4 S 4 ] cluster of the Fe protein (37). The pre-edge transition does not show an appreciable change in energy but does increase in intensity upon oxidation, indicating that there is a greater amount of 4p mixing into the 3d orbitals in the oxidized protein, consistent with a distortion in the geometry of the iron sites (38).…”

Section: Resultssupporting

confidence: 75%

“…Further evidence that the [Fe-S] center in the ⌬nifH MoFe protein is different from the P-cluster comes from the redox behavior of this mutant. The minor shifts upon oxidation to a slightly lower ratio of shortto-long Fe-Fe distances and to a slightly shorter Fe-Fe distance are more akin to the behavior of a standard [Fe 4 S 4 ] cluster than that of the P-cluster (7,8,37,48).…”

Section: Fig 3 Overlay Of the Iron K-edge Exafs (A) And Non-phaseshmentioning

confidence: 93%

See 2 more Smart Citations

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Corbett

Naderi

et al. 2004

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Nitrogenase, the enzyme system responsible for biological nitrogen fixation, is believed to utilize two unique metalloclusters in catalysis. There is considerable interest in understanding how these metalloclusters are assembled in vivo. It has been presumed that immature iron-molybdenum cofactor-deficient nitrogenase MoFe proteins contain the P-cluster, although no biosynthetic pathway for the assembly of this complex cluster has been identified as yet. Through the comparison by iron K-edge x-ray absorption edge and extended fine structure analyses of cofactor-deficient MoFe proteins resulting from nifH and nifB deletion strains of Biological nitrogen fixation, the essential conversion of atmospheric nitrogen to ammonia, is catalyzed by the nitrogenase enzyme system. Nitrogenase consists of two components, the iron (Fe) protein 1 and molybdenum-iron (MoFe) protein (reviewed in Refs. 1-5).2 Substrate reduction occurs within the MoFe protein, an ␣ 2 ␤ 2 heterotetramer that contains two unique metalloclusters, the iron-molybdenum cofactor (FeMoco) and the P-cluster. The Fe protein, which is the obligate electron donor to the MoFe protein, is a homodimer containing two nucleotide binding sites (one per subunit) and a single [Fe 4 S 4 ] cluster at the dimer interface. Nitrogenase catalysis consists of a series of Fe protein-MoFe protein complex formation and dissociation reactions in which electrons are sequentially transferred from the [Fe 4 S 4 ] cluster in the Fe protein through the P-cluster in the MoFe protein to the ultimate site of substrate reduction (FeMoco) concomitant with ATP hydrolysis by the Fe protein.There is substantial interest in elucidating the mechanism by which the metalloclusters of the MoFe protein are formed in vivo because of their importance in nitrogen fixation and because they are biologically and chemically unprecedented. FeMoco is a heterometallic double cubane consisting of one [Fe 4 S 3 ] and one [MoFe 3 S 3 ] partial cubane that are bridged by three sulfides and share a 6 -central atom of which the identity is unknown but is considered to be carbon, oxygen, or nitrogen (see Fig. 1) (6). Situated entirely in the ␣-subunit, FeMoco is attached to the protein by only two ligands, a cysteine at the terminal iron and a histidine at the opposite molybdenum, which is also coordinated by bidentate homocitrate. The Pcluster, with a topology similar to that of FeMoco, consists of a symmetric double cubane in which two [4Fe-3S] partial cubanes share a central 6 -sulfur atom (see Fig. 1). It is situated at the ␣␤ dimeric interface and is connected to the protein through six cysteine ligands, two terminal and one bridging cysteine from each subunit. The P-cluster can be reversibly oxidized from this native all-ferrous state, designated P N with indigodisulfonate (IDS) to yield a two-electron oxidized state, designated P 2ϩ or P OX . Following redox-dependent conformational change, the [Fe 4 S 4 ] cube associated with the ␣-subunit is largely unchanged, whereas the [Fe 4 S 4 ] cube associated with...

show abstract

Section: Resultssupporting

confidence: 85%

Section: Resultssupporting

confidence: 75%

Section: Fig 3 Overlay Of the Iron K-edge Exafs (A) And Non-phaseshmentioning

confidence: 93%

See 1 more Smart Citation

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Corbett

Naderi

et al. 2004

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, there are some differences in detail. There is no indication of a core distortion that, from extended x-ray absorption fine structure analysis, affords two short (2.52 Å) plus one long (2.77 Å) Fe-Fe distances and one short (2.29 Å) plus three long (2.35-2.37 Å) Fe-S distances (9). Further, there is no evidence from Mössbauer spectroscopy of a single iron site with a large quadrupole splitting that could be associated with discrete Fe II .…”

Section: Resultsmentioning

confidence: 94%

Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe ₄ S ₄ ] ⁰ cluster of the nitrogenase iron protein

Scott

Berlinguette²,

Holm³

et al. 2005

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

View full text Add to dashboard Cite

The synthetic cubane-type iron-sulfur clusters [Fe4S4(SR)4] z form a four-member electron transfer series (z ‫؍‬ 3؊, 2؊, 1؊, and 0), all members of which except that with z ‫؍‬ 0 have been isolated and characterized. (14). Evidence has been presented for a two-electron transfer by the fully reduced Fe protein in nitrogenase catalysis (15). Here, we demonstrate that the heretofore elusive all-ferrous state in a cubane-type cluster can be isolated in substance. Materials and Methods

show abstract

“…The discovery (4) and characterization (5)(6)(7)(8)(9)(10)(11)(12) of an [Fe 4 S 4 ] 0 Av2 has raised questions regarding how nitrogenase functions (13)(14)(15) because the 2ϩ͞0 couple involves two electrons instead of one (5)(6)(7) to decrease the optimal ATP requirement 2-fold. This energy efficiency makes the study of [Fe 4 (17), and an E m ϭ -790 mV (18) was estimated for the 1ϩ͞0 couple, which is in line with E m estimates of all-ferrous Fe-S clusters by using discrete Fourier transform calculations (19).…”

mentioning

confidence: 99%

Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state

Lowery

Wilson

Zhang

et al. 2006

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

106

View full text Add to dashboard Cite

(17), and an E m ϭ -790 mV (18) was estimated for the 1ϩ͞0 couple, which is in line with E m estimates of all-ferrous Fe-S clusters by using discrete Fourier transform calculations (19). Indeed, this latter study raised the question of whether [Fe 4 S 4 ] 0 Av2 can even be made in vivo (1). A value of -790 mV is not consistent with turnover potential measured by Ti(III) and other reductants and with reported potentials for the Ti(IV)͞Ti(III) couple (7,20). If an E m ϭ -460 mV for the 1ϩ͞0 couple (16)

show abstract

All-Ferrous Titanium(III) Citrate Reduced Fe Protein of Nitrogenase: An XAS Study of Electronic and Metrical Structure

Cited by 86 publications

References 18 publications

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe ₄ S ₄ ] ⁰ cluster of the nitrogenase iron protein

Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state

Contact Info

Product

Resources

About

All-Ferrous Titanium(III) Citrate Reduced Fe Protein of Nitrogenase: An XAS Study of Electronic and Metrical Structure

Cited by 86 publications

References 18 publications

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Comparison of Iron-Molybdenum Cofactor-deficient Nitrogenase MoFe Proteins by X-ray Absorption Spectroscopy

Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe 4 S 4 ] 0 cluster of the nitrogenase iron protein

Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state

Contact Info

Product

Resources

About

Initial synthesis and structure of an all-ferrous analogue of the fully reduced [Fe ₄ S ₄ ] ⁰ cluster of the nitrogenase iron protein