Ferredoksiin

Ferredoksiin is a term used in some languages to refer to ferredoxins, a family of small iron-sulfur proteins that function as soluble electron carriers in a variety of biological redox reactions. In English-language literature, the standard name is ferredoxin; ferredoksiin may appear as a transliteration or regional spelling.

Structure and chemistry

Most ferredoxins are compact proteins, typically about 100 to 120 amino acids in length, and they coordinate one or more iron-sulfur clusters, commonly [2Fe-2S] or [4Fe-4S]. The iron-sulfur cluster geometry and surrounding amino acid ligands, especially cysteine residues, determine their redox properties and stability. Ferredoxins exhibit a range of redox potentials chosen to match their physiological roles.

Biological function

Ferredoksins act as one-electron couriers in electron transport chains. In photosynthesis, chloroplast and cyanobacterial ferredoxins transfer electrons from photosystem I to ferredoxin-NADP+ reductase (FNR) to produce NADPH. In bacteria and archaea, ferredoxins participate in diverse pathways, including fatty acid synthesis, nitrogen fixation, and anaerobic respiration, by bridging electrons between different enzymatic partners.

Distribution and diversity

Ferredoxins are widespread across life, including plants, algae, cyanobacteria, bacteria, and some archaea. They exist in several types, categorized by their cluster composition and organismal context, which tailor their redox potential and interaction surfaces for specific pathways.

Applications and significance

Beyond their biological roles, ferredoxins are widely used in biochemical research as model electron carriers and in vitro catalysts. They also feature in synthetic biology and metabolic engineering efforts to connect redox reactions in engineered pathways.

See also: ferredoxin, iron-sulfur proteins, electron transfer.