Electron Transfer Mechanisms in Ferredoxin-Linked Reductases

Ferredoxin-linked reductases are a diverse family of flavoenzymes that mediate electron transfer between low-potential iron–sulfur carriers and a wide range of oxidoreductase partners. Mechanistic diversity arises from the interplay of one-electron and two-electron (hydride) transfer pathways, precise tuning of redox potentials and dynamic protein–protein interactions. In photosynthetic organisms, small [2Fe–2S] ferredoxins ferry electrons from photosystem I to ferredoxin–NADP⁺ oxidoreductase (FNR) for NADPH synthesis. In non-photosynthetic bacteria and eukaryotic systems, ferredoxin-linked reductases interface with hydrogenases, sulfite reductases, cytochrome P450s and other enzymes to support energy conversion, nutrient assimilation and redox homeostasis. Central to these processes are iron–sulfur clusters or flavin prosthetic groups, which cycle through oxidised, semiquinone and fully reduced states. Recent structural, spectroscopic and kinetic studies have begun to reveal how redox-dependent conformational changes, electrostatic docking surfaces and transient semiquinone intermediates govern electron-transfer rates and specificity. Elucidation of these mechanisms is crucial for engineering biofuel production, biocatalytic detoxification and artificial photosynthetic devices.

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Electron Transfer Mechanisms in Ferredoxin-Linked Reductases publication trend

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Technical terms

Ferredoxin: A small iron–sulfur protein that donates single electrons in photosynthetic and metabolic pathways.

Ferredoxin–NADP⁺ oxidoreductase (FNR): A flavoprotein enzyme that catalyses hydride (two-electron) transfer between ferredoxin and NADP⁺, yielding NADPH.

Iron–sulfur cluster: A prosthetic group composed of iron and sulphur atoms that enables one-electron redox chemistry.

Hydride transfer: A two-electron transfer process in which a hydride ion (H⁻) moves from a donor to an acceptor molecule.

Semiquinone: A one-electron reduced intermediate state of a flavin cofactor that participates in sequential electron transfers.

References

1. Probing the ferredoxin:hydrogenase electron transfer complex by infrared difference spectroscopy. Chemical Science (2025).
2. The Role of the si-Face Tyrosine of a Homodimeric Ferredoxin-NADP+ Oxidoreductase from Bacillus subtilis during Complex Formation and Redox Equivalent Transfer with NADP+/H and Ferredoxin. Antioxidants (2023).
3. Roles of Ferredoxin-NADP+ Oxidoreductase and Flavodoxin in NAD(P)H-Dependent Electron Transfer Systems. Antioxidants (2022).
4. Comparison of the Electrostatic Binding Sites on the Surface of Ferredoxin for Two Ferredoxin-dependent Enzymes, Ferredoxin-NADP+ Reductase and Sulfite Reductase*. Journal of Biological Chemistry (1999).