Editing Ferredoxin (section)

{{Short description|Iron–sulfur proteins that mediate electron transfer in metabolic reactions}}
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'''Ferredoxins''' (from [[Latin]] ''ferrum'': [[iron]] + [[redox]], often abbreviated "fd") are [[iron–sulfur protein]]s that mediate [[electron transfer]] in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the [[DuPont]] Co. and applied to the "iron protein" first purified in 1962 by Mortenson, Valentine, and Carnahan from the [[anaerobic organism|anaerobic]] bacterium ''[[Clostridium pasteurianum]]''.<ref name="pmid14476372">{{cite journal | vauthors = Mortenson LE, Valentine RC, Carnahan JE | title = An electron transport factor from Clostridium pasteurianum | journal = Biochemical and Biophysical Research Communications | volume = 7 | issue = 6 | pages = 448–52 | date = June 1962 | pmid = 14476372 | doi = 10.1016/0006-291X(62)90333-9 }}</ref><ref name="pmid14244728">{{cite journal | vauthors = Valentine RC | title = Bacterial Ferredoxin | journal = Bacteriological Reviews | volume = 28 | issue = 4 | pages = 497–517 | date = December 1964 | pmid = 14244728 | pmc = 441251 | doi = 10.1128/MMBR.28.4.497-517.1964 }}</ref>

Another redox protein, isolated from spinach [[chloroplast]]s, was termed "chloroplast ferredoxin".<ref name="pmid14039612">{{cite journal | vauthors = Tagawa K, Arnon DI | title = Ferredoxins as electron carriers in photosynthesis and in the biological production and consumption of hydrogen gas | journal = Nature | volume = 195 | issue = 4841 | pages = 537–43 | date = August 1962 | pmid = 14039612 | doi = 10.1038/195537a0 | s2cid = 4213017 | bibcode = 1962Natur.195..537T }}</ref> The chloroplast ferredoxin is involved in both cyclic and non-cyclic [[photophosphorylation]] reactions of [[photosynthesis]]. In non-cyclic photophosphorylation, ferredoxin is the last electron acceptor thus reducing the enzyme NADP<sup>+</sup> reductase.  It accepts electrons produced from [[sunlight]]-[[Electron excitation|excited]] [[chlorophyll]] and transfers them to the enzyme ferredoxin: NADP<sup>+</sup> oxidoreductase {{EC number|1.18.1.2}}.

Ferredoxins are small proteins containing [[iron]] and [[sulfur]] atoms organized as [[iron–sulfur cluster]]s. These biological "[[capacitors]]" can accept or discharge electrons, with the effect of a change in the oxidation state of the iron atoms between +2 and +3. In this way, ferredoxin acts as an electron transfer agent in biological [[redox]] reactions.

Other [[bioinorganic]] electron transport systems include [[rubredoxin]]s, [[cytochromes]], [[blue copper protein]]s, and the structurally related [[Rieske protein]]s.

Ferredoxins can be classified according to the nature of their iron–sulfur clusters and by sequence similarity.