The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components

Siemann S, Schneider K, Drottboom M, Müller A (2002)
EUROPEAN JOURNAL OF BIOCHEMISTRY 269(6): 1650-1661.

Journal Article | Published | English

No fulltext has been uploaded

Author
; ; ;
Abstract
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 = 1/2 EPR signals deriving from oxidized states of the P-cluster were detected: (1) a rhombic signal (g = 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(ii) = 2.00, g(perpendicular to) = 1.90) with almost identical redox properties and (3) a second rhombic signal (g = 2.03, 2.00, 1.90) at higher redox potentials ( > 100 mV). While the 'low-potential' rhombic signal and the axial signal have been both attributed to the one-electron-oxidized P-cluster (P1+) present in two conformationally different proteins, the 'high-potential' rhombic signal has been suggested rather to derive from the P3+ state. Upon oxidation, the FeFe protein (Rc1(Fe)) exibited three significant S = 1/2 EPR signals as well. However, the Re I F, 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 = 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 = 1.86. (c) A very narrow rhombic EPR signal at g = 2.00, 1.98 and 1.96 appeared at positive redox potentials (E-m = 80 mV, intensity maximum at 160 mV). Another novel S = 1/2 signal at g = 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 'turnover signal' nor any other S = 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.
Publishing Year
ISSN
PUB-ID

Cite this

Siemann S, Schneider K, Drottboom M, Müller A. The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components. EUROPEAN JOURNAL OF BIOCHEMISTRY. 2002;269(6):1650-1661.
Siemann, S., Schneider, K., Drottboom, M., & Müller, A. (2002). The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components. EUROPEAN JOURNAL OF BIOCHEMISTRY, 269(6), 1650-1661.
Siemann, S., Schneider, K., Drottboom, M., and Müller, A. (2002). The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components. EUROPEAN JOURNAL OF BIOCHEMISTRY 269, 1650-1661.
Siemann, S., et al., 2002. The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components. EUROPEAN JOURNAL OF BIOCHEMISTRY, 269(6), p 1650-1661.
S. Siemann, et al., “The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components”, EUROPEAN JOURNAL OF BIOCHEMISTRY, vol. 269, 2002, pp. 1650-1661.
Siemann, S., Schneider, K., Drottboom, M., Müller, A.: The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components. EUROPEAN JOURNAL OF BIOCHEMISTRY. 269, 1650-1661 (2002).
Siemann, S, Schneider, Klaus, Drottboom, M, and Müller, Achim. “The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatus - A comparative study on the redox properties of the metal clusters present in the dinitrogenase components”. EUROPEAN JOURNAL OF BIOCHEMISTRY 269.6 (2002): 1650-1661.
This data publication is cited in the following publications:
This publication cites the following data publications:

2 Citations in Europe PMC

Data provided by Europe PubMed Central.

Nitrogenase and homologs.
Hu Y, Ribbe MW., J. Biol. Inorg. Chem. 20(2), 2015
PMID: 25491285
Catalytic reduction of dinitrogen to ammonia by molybdenum: theory versus experiment.
Schrock RR., Angew. Chem. Int. Ed. Engl. 47(30), 2008
PMID: 18537212

51 References

Data provided by Europe PubMed Central.

The electronic structure of FeS centres in proteins and models. A contribution to the understanding of their electron transfer properties
Bertini, Struct. Bonding 83(), 1995

Export

0 Marked Publications

Open Data PUB

Web of Science

View record in Web of Science®

Sources

PMID: 11895435
PubMed | Europe PMC

Search this title in

Google Scholar