Spectroscopic characterization of the novel iron-sulfur cluster in Pyrococcus furiosus ferredoxin
| Autor: | Michael K. Johnson, Andrzej T. Kowal, Weiguang Fu, Jae-Bum Park, Michael W. W. Adams, Shigetoshi Aono, Richard C. Conover |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
inorganic chemicals
Circular dichroism biology Analytical chemistry Iron–sulfur cluster Cell Biology biology.organism_classification Biochemistry law.invention chemistry.chemical_compound symbols.namesake Crystallography chemistry law symbols Cluster (physics) Pyrococcus furiosus Ferricyanide Raman spectroscopy Electron paramagnetic resonance Molecular Biology Ferredoxin |
| Zdroj: | Journal of Biological Chemistry. 265:8533-8541 |
| ISSN: | 0021-9258 |
| DOI: | 10.1016/s0021-9258(19)38921-5 |
| Popis: | Pyrococcus furiosus ferredoxin is the only known example of a ferredoxin containing a single [4Fe-4S] cluster that has non-cysteinyl ligation of one iron atom, as evidenced by the replacement of a ligating cysteine residue by an aspartic acid residue in the amino acid sequence. The properties of the iron-sulfur cluster in both the aerobically and anaerobically isolated ferredoxin have been characterized by EPR, magnetic circular dichroism, and resonance Raman spectroscopies. The anaerobically isolated ferrodoxin contains a [4Fe-4S]+,2+ cluster with anomalous properties in both the oxidized and reduced states which are attributed to aspartate and/or hydroxide coordination of a specific iron atom. In the reduced form, the cluster exists with a spin mixture of S = 1/2 (20%) and S = 3/2 (80%) ground states. The dominant S = 3/2 form has a unique EPR spectrum that can be rationalized by an S = 3/2 spin Hamiltonian with E/D = 0.22 and D = +3.3 +/- 0.2 cm-1. The oxidized cluster has an S = 0 ground state, and the resonance Raman spectrum is characteristic of a [4Fe-4S]2+ cluster except for the unusually high frequency for the totally symmetric breathing mode of the [4Fe-4S] core, 342 cm-1. Comparison with Raman spectra of other [4Fe-4S]2+ centers suggests that this behavior is diagnostic of anomalous coordination of a specific iron atom. The iron-sulfur cluster is shown to undergo facile and quantitative [4Fe-4S] in equilibrium [3Fe-4S] interconversion, and the oxidized and reduced forms of the [3Fe-4S] cluster have S = 1/2 and S = 2 ground states, respectively. In both redox states the [3Fe-4S]0,+ cluster exhibits spectroscopic properties analogous to those of similar clusters in other bacterial ferredoxins, suggesting non-cysteinyl coordination for the iron atom that is removed by ferricyanide oxidation. Aerobic isolation induces partial degradation of the [4Fe-4S] cluster to yield [3Fe-4S] and possibly [2Fe-2S] centers. Evidence is presented to show that only the [4Fe-4S] form of this ferredoxin exists in vivo. |
| Databáze: | OpenAIRE |
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