Structural redox control in a 7Fe ferredoxin isolated from Desulfovibrio alaskensis

• Published in: Bioelectrochemistry (Amsterdam, Netherlands) Netherlands), 2011-08, Vol.82 (1), p.22-28
• Main Authors: Grazina, Raquel, de Sousa, Patrícia M. Paes, Brondino, Carlos D., Carepo, Marta S.P., Moura, Isabel, Moura, José J.G.
• Format: Article
• Language: English
• Subjects: 7Fe ferredoxins; Bacterial Proteins - chemistry; Bacterial Proteins - isolation & purification; Desulfovibrio; Desulfovibrio - chemistry; Desulfovibrio africanus; Desulfovibrio bacteria; Desulfovibrio vulgaris; Electrochemical Techniques; Electrochemistry; Electron Spin Resonance Spectroscopy; Electron Transport; Ferredoxins - chemistry; Ferredoxins - isolation & purification; Iron–sulfur clusters; Oxidation-Reduction
• ISSN: 1567-5394; 1878-562X
• DOI: 10.1016/j.bioelechem.2011.04.005

The redox behaviour of a ferredoxin (Fd) from Desulfovibrio alaskensis was characterized by electrochemistry. The protein was isolated and purified, and showed to be a tetramer containing one [3Fe–4S] and one [4Fe–4S] centre. This ferredoxin has high homology with FdI from Desulfovibrio vulgaris Miyazaki and Hildenborough and FdIII from Desulfovibrio africanus. From differential pulse voltammetry the following signals were identified: [3Fe-4S] + 1/0 (E 0′ = − 158 ± 5 mV); [4Fe–4S] + 2/+1 (E 0′ = − 474 ± 5 mV) and [3Fe–4S] 0/− 2 (E 0′ = − 660 ± 5 mV). The effect of pH on these signals showed that the reduced [3Fe–4S] 0 cluster has a p Kʹ red ′ = 5.1 ± 0.1, the [4Fe–4S] + 2/+1 centre is pH independent, and the [3Fe–4S] 0/−2 reduction is accompanied by the binding of two protons. The ability of the [3Fe–4S] 0 cluster to be converted into a new [4Fe–4S] cluster was proven. The redox potential of the original [4Fe–4S] centre showed to be dependent on the formation of the new [4Fe-4S] centre, which results in a positive shift ( ca. 70 mV) of the redox potential of the original centre. Being most [Fe–S] proteins involved in electron transport processes, the electrochemical characterization of their clusters is essential to understand their biological function. Complementary EPR studies were performed. [Display omitted] ► D. alaskensis Fd is a 7Fe protein containing one [3Fe–4S] and one [4Fe–4S] cluster. ► The [3Fe–4S] 0 cluster can be converted into a new [4Fe–4S] cluster. ► E 0ʹ of the original [4Fe–4S] centre depends on the formation of the new 4Fe centre.