The Fe-Only Nitrogenase From Rhodobacter capsulatus: 2. The FeFe Protein Metal Centers Probed by EXAFS and Mössbauer Spectroscopy

Krahn, Eugen; Weiss, B. J. R.; Kröckel, Monika; Cramer, Stephen P.; Trautwein, A. X.; Schneider, Klaus; Müller, Achim

doi:10.1007/978-94-011-5159-7_16

Cited by 3 publications

(2 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A recent 57 Fe‐Mössbauer‐/Fe‐EXAFS study on the FeFe protein from R. capsulatus provided strong evidence that: (a) the FeFe cofactor is diamagnetic in the Na 2 S 2 O 4 ‐reduced state containing 4Fe II and 4Fe III centers, and (b) the main structural feature of the FeMoco, the central trigonal prismatic arrangement of Fe atoms, is also present in the FeFe cofactor, thus indicating a structural homology between both cofactor types [20,21].…”

mentioning

confidence: 99%

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

Siemann¹,

Schneider

Dröttboom³

et al. 2002

European Journal of Biochemistry

View full text Add to dashboard Cite

The dinitrogenase component proteins of the conventional Mo nitrogenase (MoFe protein) and of the alternative Fe-only nitrogenase (FeFe protein) were both isolated and purified from Rhodobacter capsulatus, redox-titrated according to the same procedures and subjected to an EPR spectroscopic comparison. In the course of an oxidative titration of the MoFe protein (Rc1 Mo ) three significant S ¼ 1/2 EPR signals deriving from oxidized states of the P-cluster were detected: (1) a rhombic signal (g ¼ 2.07, 1.96 and 1.83), which showed a bell-shaped redox curve with midpoint potentials (E m ) of )195 mV (appearance) and )30 mV (disappearance), (2) an axial signal (g || ¼ 2.00, g^¼ 1.90) with almost identical redox properties and (3) a second rhombic signal (g ¼ 2.03, 2.00, 1.90) at higher redox potentials (> 100 mV). While the Ôlow-potentialÕ rhombic signal and the axial signal have been both attributed to the one-electron-oxidized P-cluster (P 1+ ) present in two conformationally different proteins, the Ôhigh-potentialÕ rhombic signal has been suggested rather to derive from the P 3+ state. Upon oxidation, the FeFe protein (Rc1 Fe ) exibited three significant S ¼ 1/2 EPR signals as well. However, the Rc1 Fe signals strongly deviated from the MoFe protein signals, suggesting that they cannot simply be assigned to different P-cluster states. (a) The most prominent feature is an unusually broad signal at g ¼ 2.27 and 2.06, which proved to be fully reversible and to correlate with catalytic activity. The cluster giving rise to this signal appears to be involved in the transfer of two electrons. The midpoint potentials determined were: )80 mV (appearance) and 70 mV (disappearance). (b) Under weakly acidic conditions (pH 6.4) a slightly altered EPR signal occurred. It was characterized by a shift of the g values to 2.22 and 2.05 and by the appearance of an additional negative absorption-shaped peak at g ¼ 1.86. (c) A very narrow rhombic EPR signal at g ¼ 2.00, 1.98 and 1.96 appeared at positive redox potentials (E m ¼ 80 mV, intensity maximum at 160 mV). Another novel S ¼ 1/2 signal at g ¼ 1.96, 1.92 and 1.77 was observed on further, enzymatic reduction of the dithionite-reduced state of Rc1 Fe with the dinitrogenase reductase component (Rc2 Fe ) of the same enzyme system (turnover conditions in the presence of N 2 and ATP). When the Rc1 Mo protein was treated analogously, neither this Ôturnover signalÕ nor any other S ¼ 1/2 signal were detectable. All Rc1 Fe -specific EPR signals detected are discussed and tentatively assigned with special consideration of the reference spectra obtained from Rc1 Mo preparations.

show abstract

mentioning

confidence: 99%

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

Siemann¹,

Schneider

Dröttboom³

et al. 2002

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…156 Subsequent study of the biological nitrogenases has led to the conclusion that they are likely structurally (and potentially mechanistically) similar. 11,36,[157][158][159] In particular, recent spectroscopic and crystallographic evidence has begun to emerge in both the MoFe and VFe nitrogenases that the site of N 2 -binding and functionalization is likely to be at an Fe site. In particular, both the Rees and Einsle groups have obtained structures that demonstrate sulfide-loss and ligand binding between Fe 2 and Fe 6 (Figure 38).…”

Section: Achieving Nitrogen Fixation Catalysis At Fementioning

confidence: 99%

Catalytic N₂-to-NH₃(or -N₂H₄) Conversion by Well-Defined Molecular Coordination Complexes

2020

View full text Add to dashboard Cite

Nitrogen fixation, the six-electron/six-proton reduction of N 2 , to give NH 3 , is one of the most challenging and important chemical transformations. Notwithstanding the barriers associated with this reaction, significant progress has been made in developing molecular complexes that reduce N 2 into its bioavailable form, NH 3 . This progress is driven by the dual aims of better understanding biological nitrogenases and improving upon industrial nitrogen fixation. In this review, we highlight both mechanistic understanding of nitrogen fixation that has been developed, as well as advances in yields, efficiencies, and rates that make molecular alternatives to nitrogen fixation increasingly appealing. We begin with a historical discussion of N 2 functionalization chemistry that traverses a timeline of events leading up to the discovery of the first bona fide molecular catalyst system and follow with a comprehensive overview of d-block compounds that have been targeted as catalysts up to and including 2019. We end with a summary of lessons learned from this significant research effort and last offer a discussion of key remaining challenges in the field.

show abstract

The Mechanism of Molybdenum Nitrogenase: An Overview

Burgess

Nitrogen Fixation: From Molecules to Crop Productivity

View full text Add to dashboard Cite

The Fe-Only Nitrogenase From Rhodobacter capsulatus: 2. The FeFe Protein Metal Centers Probed by EXAFS and Mössbauer Spectroscopy

Cited by 3 publications

References 5 publications

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

Catalytic N₂-to-NH₃(or -N₂H₄) Conversion by Well-Defined Molecular Coordination Complexes

The Mechanism of Molybdenum Nitrogenase: An Overview

Contact Info

Product

Resources

About

The Fe-Only Nitrogenase From Rhodobacter capsulatus: 2. The FeFe Protein Metal Centers Probed by EXAFS and Mössbauer Spectroscopy

Cited by 3 publications

References 5 publications

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

The Fe‐only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus

Catalytic N2-to-NH3(or -N2H4) Conversion by Well-Defined Molecular Coordination Complexes

The Mechanism of Molybdenum Nitrogenase: An Overview

Contact Info

Product

Resources

About

Catalytic N₂-to-NH₃(or -N₂H₄) Conversion by Well-Defined Molecular Coordination Complexes