Reduction Potentials of [FeFe]-Hydrogenase Accessory Iron-Sulfur Clusters Provide Insights into the Energetics of Proton Reduction Catalysis

Jacob H. Artz, David W. Mulder, Michael W. Ratzloff, Carolyn E. Lubner, Oleg A. Zadvornyy, Axl X. Levan, S. Garrett Williams, Michael W.W. Adams, Anne K. Jones, Paul W. King, John W. Peters

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

An [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, is a model system for biological H2 activation. In addition to the catalytic H-cluster, CpI contains four accessory iron-sulfur [FeS] clusters in a branched series that transfer electrons to and from the active site. In this work, potentiometric titrations have been employed in combination with electron paramagnetic resonance (EPR) spectroscopy at defined electrochemical potentials to gain insights into the role of the accessory clusters in catalysis. EPR spectra collected over a range of potentials were deconvoluted into individual components attributable to the accessory [FeS] clusters and the active site H-cluster, and reduction potentials for each cluster were determined. The data suggest a large degree of magnetic coupling between the clusters. The distal [4Fe-4S] cluster is shown to have a lower reduction potential (∼ < -450 mV) than the other clusters, and molecular docking experiments indicate that the physiological electron donor, ferredoxin (Fd), most favorably interacts with this cluster. The low reduction potential of the distal [4Fe-4S] cluster thermodynamically restricts the Fdox/Fdred ratio at which CpI can operate, consistent with the role of CpI in recycling Fdred that accumulates during fermentation. Subsequent electron transfer through the additional accessory [FeS] clusters to the H-cluster is thermodynamically favorable.

Original languageEnglish
Pages (from-to)9544-9550
Number of pages7
JournalJournal of the American Chemical Society
Volume139
Issue number28
DOIs
Publication statusPublished - Jul 19 2017

Fingerprint

Hydrogenase
Accessories
Catalysis
Sulfur
Protons
Iron
Electron Spin Resonance Spectroscopy
Electrons
Catalytic Domain
Paramagnetic resonance
Ferredoxins
Biological Models
Clostridium
Recycling
Magnetic couplings
Fermentation
Spectrum Analysis
Titration
Chemical activation
Spectroscopy

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Reduction Potentials of [FeFe]-Hydrogenase Accessory Iron-Sulfur Clusters Provide Insights into the Energetics of Proton Reduction Catalysis. / Artz, Jacob H.; Mulder, David W.; Ratzloff, Michael W.; Lubner, Carolyn E.; Zadvornyy, Oleg A.; Levan, Axl X.; Williams, S. Garrett; Adams, Michael W.W.; Jones, Anne K.; King, Paul W.; Peters, John W.

In: Journal of the American Chemical Society, Vol. 139, No. 28, 19.07.2017, p. 9544-9550.

Research output: Contribution to journalArticle

Artz, JH, Mulder, DW, Ratzloff, MW, Lubner, CE, Zadvornyy, OA, Levan, AX, Williams, SG, Adams, MWW, Jones, AK, King, PW & Peters, JW 2017, 'Reduction Potentials of [FeFe]-Hydrogenase Accessory Iron-Sulfur Clusters Provide Insights into the Energetics of Proton Reduction Catalysis', Journal of the American Chemical Society, vol. 139, no. 28, pp. 9544-9550. https://doi.org/10.1021/jacs.7b02099
Artz, Jacob H. ; Mulder, David W. ; Ratzloff, Michael W. ; Lubner, Carolyn E. ; Zadvornyy, Oleg A. ; Levan, Axl X. ; Williams, S. Garrett ; Adams, Michael W.W. ; Jones, Anne K. ; King, Paul W. ; Peters, John W. / Reduction Potentials of [FeFe]-Hydrogenase Accessory Iron-Sulfur Clusters Provide Insights into the Energetics of Proton Reduction Catalysis. In: Journal of the American Chemical Society. 2017 ; Vol. 139, No. 28. pp. 9544-9550.
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