Heterometallic [AgFe3S4] ferredoxin variants: Synthesis, characterization, and the first crystal structure of an engineered heterometallic iron-sulfur protein

Maja Martic, Ida Noémi Jakab-Simon, Lærke Tvedebrink Haahr, Wilfred Raymond Hagen, Hans Erik Mølager Christensen

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)

Abstract

Heterometallic [AgFe3S4] iron-sulfur clusters assembled in wild-type Pyrococcus furiosus ferredoxin and two variants, D14C and D14H, are characterized. The crystal structure of the [AgFe3S 4] D14C variant shows that the silver(I) ion is indeed part of the cluster and is coordinated to the thiolate group of residue 14. Cyclic voltammetry shows one redox pair with a reduction potential of +220 mV versus the standard hydrogen electrode which is assigned to the [AgFe3S 4]2+/+ couple. The oxidized form of the [AgFe 3S4] D14C variant is stable in the presence of dioxygen, whereas the oxidized forms of the [AgFe3S4] wild type and D14H variants convert to the [Fe3S4] ferredoxin form. The monovalent d 10 silver(I) ion stabilizes the [Fe3S 4]+/0 cluster fragment, as opposed to divalent d 10 metal ions, resulting in more than 0.4 V difference in reduction potentials between the silver(I) and, e.g., zinc(II) heterometallic [MFe 3S4] ferredoxins. The trend in reduction potentials for the variants containing the [AgFe3S4] cluster is wild type ≤ D14C < D14H and shows the same trend as reported for the variants containing the [Fe3S4] cluster, but is different from the D14C < D14H < wild type trend reported for the [Fe4S 4] ferredoxin. The similarity in the reduction potential trend for the variants containing the heterometallic [AgFe3S4] cluster and the [Fe3S4] cluster can be rationalized in terms of the electrostatic influence of the residue 14 side chains, rather than the dissociation constant of this residue, as is the case for [Fe 4S4] ferredoxins. The trends in reduction potentials are in line with there being no electronic coupling between the silver(I) ion and the Fe3S4 fragment.

Original languageEnglish
Pages (from-to)261-276
JournalJournal of Biological Inorganic Chemistry
Volume18
Issue number2
DOIs
Publication statusPublished - 2013

Keywords

  • Ferredoxin
  • Heterometallic
  • Mass spectrometry
  • Pyrococcus furiosus
  • Silver

Fingerprint Dive into the research topics of 'Heterometallic [AgFe<sub>3</sub>S<sub>4</sub>] ferredoxin variants: Synthesis, characterization, and the first crystal structure of an engineered heterometallic iron-sulfur protein'. Together they form a unique fingerprint.

  • Cite this