Ferredoxin 1162678 220985687 2008-06-22T14:57:53Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{protein |name=ferredoxin 1 |caption= |image= |width= |HGNCid=3638 |Symbol=FDX1 |AltSymbols=FDX |EntrezGene=2230 |OMIM= |RefSeq=NM_004109 |UniProt= |PDB= |ECnumber= |Chromosome=11 |Arm=q |Band=22.3 |LocusSupplementaryData= }} {{protein |name=ferredoxin 2 |caption= |image= |width= |HGNCid=3639 |Symbol=FDX2 |AltSymbols= |EntrezGene=2143 |OMIM= |RefSeq= |UniProt= |PDB= |ECnumber= |Chromosome= |Arm= |Band= |LocusSupplementaryData= }} '''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 bacterium ''Clostridium pasteurianum'' (Valentine, 1964). Another redox protein, isolated from spinach [[chloroplast]]s by Tagawa and Arnon in 1962, was termed "chloroplast ferredoxin." 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 and reduces the enzyme NADP<sup>+</sup> reductase. It accepts electrons produced from [[sunlight]]-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, the effect being change in the oxidation states (+2 or +3) of the iron atoms. This way, ferredoxin acts as electron transfer agents in biological [[redox]] reactions. Other [[bioinorganic]] electron transport systems include [[rubredoxin]]s, [[cytochromes]], blue copper proteins, and the structurally related [[Rieske protein]]s. Ferredoxins can be classified according to the nature of their [[iron-sulfur cluster]]s and by sequence similarity. == Fe<sub>2</sub>S<sub>2</sub> ferredoxins == [[Image:Fe2S2.png|frame|none|''Structural representation of an Fe<sub>2</sub>S<sub>2</sub> ferredoxin.'']] === Plant-type ferredoxins === One group of ferredoxins, originally found in [[chloroplast]] membranes, has been termed "chloroplast-type" or "plant-type". The active center is a [Fe<sub>2</sub>S<sub>2</sub>] cluster, where the iron atoms are tetrahedrally coordinated both by inorganic sulfur atoms and by sulfurs provided by four conserved [[cysteine]] (Cys) residues. In chloroplasts, Fe<sub>2</sub>S<sub>2</sub> ferredoxins function as electron carriers in the [[Photophosphorylation|photosynthetic electron transport chain]] and as electron donors to various cellular proteins, such as glutamate synthase, nitrate reductase and sulfite reductase. In hydroxylating bacterial dioxygenase systems, they serve as intermediate electron-transfer carriers between reductase flavoproteins and oxygenase. === Adrenodoxin-type ferredoxins === Adrenodoxin, putidaredoxin and terpredoxin are soluble Fe<sub>2</sub>S<sub>2</sub> proteins that act as single electron carriers. In mitochondrial monooxygenase systems, adrenodoxin transfers an electron from NADPH:adrenodoxin reductase to membrane-bound [[cytochrome P450]]. In bacteria, putidaredoxin and terpredoxin serve as electron carriers between corresponding NADH-dependent ferredoxin reductases and soluble P450s. The exact functions of other members of this family are not known, although ''Escherichia coli'' Fdx is shown to be involved in biogenesis of Fe-S clusters. Despite low sequence similarity between adrenodoxin-type and plant-type ferredoxins, the two classes have a similar folding topology. === Thioredoxin-like ferredoxins === The Fe<sub>2</sub>S<sub>2</sub> ferredoxin from ''Clostridium pasteurianum'' (''Cp''2FeFd) has been recognized as distinct protein family on the basis of its amino acid sequence, spectroscopic properties of its iron-sulfur cluster and the unique ligand swapping ability of two cysteine ligands to the [Fe<sub>2</sub>S<sub>2</sub>] cluster. Although the physiological role of this ferredoxin remains unclear, a strong and specific intraction of ''Cp''2FeFd with the molybdenum-iron protein of [[nitrogenase]] has been revealed. Homologous ferredoxins from ''Azotobacter vinelandii'' (''Av''2FeFdI) and ''Aquifex aeolicus'' (''Aa''Fd) have been characterized. The crystal structure of ''Aa''Fd has been solved. ''Aa''Fd exists as a dimer. The structure of ''Aa''Fd monomer is different from other Fe<sub>2</sub>S<sub>2</sub> ferredoxins. The fold belongs to the α+β class, with first four β-strands and two α-helices adopting a variant of the [[thioredoxin]] fold. [[Image:Fe3S4.png|thumb|300px|''Structural representation of an Fe<sub>3</sub>S<sub>4</sub> ferredoxin.'']] == Fe<sub>4</sub>S<sub>4</sub> and Fe<sub>3</sub>S<sub>4</sub> ferredoxins == The [Fe<sub>4</sub>S<sub>4</sub>] ferredoxins may be further subdivided into low-potential (bacterial-type) and [[HIPIP|high-potential (HiPIP) ferredoxins]]. Low- and high-potential ferredoxins are related by the following redox scheme: [[Image:FdRedox.png|center|500px]] The formal oxidation numbers of the iron ions can be [2Fe<sup>3+</sup>, 2Fe<sup>2+</sup>] or [1Fe<sup>3+</sup>, 3Fe<sup>2+</sup>] in low-potential ferredoxins. The oxidation numbers of the iron ions in high-potential ferredoxins can be [3Fe<sup>3+</sup>, 1Fe<sup>2+</sup>] or [2Fe<sup>3+</sup>, 2Fe<sup>2+</sup>]. === Bacterial-type ferredoxins === A group of Fe<sub>4</sub>S<sub>4</sub> ferredoxins, originally found in bacteria, has been termed "bacterial-type". Bacterial-type ferredoxins may in turn be subdivided into further groups, based on their sequence properties. Most contain at least one conserved domain, including four cysteine residues that bind to a [Fe<sub>4</sub>S<sub>4</sub>] cluster. In ''Pyrococcus furiosus'' Fe<sub>4</sub>S<sub>4</sub> ferredoxin, one of conserved Cys residues is substituted with aspartic acid. During the evolution of bacterial-type ferredoxins, intrasequence gene duplication, transposition and fusion events occurred, resulting in the appearance of proteins with multiple iron-sulfur centers. In some bacterial ferredoxins, one of the duplicated domains has lost one or more of the four conserved Cys residues. These domains have either lost their iron-sulfur binding property, or bind to a [Fe<sub>3</sub>S<sub>4</sub>] cluster instead of a [Fe<sub>4</sub>S<sub>4</sub>] cluster. 3-D structures are known for a number of monocluster and dicluster bacterial-type ferredoxins. The fold belongs to the α+β class, with 2-7 α-helices and four β-strands forming a barrel-like structure, and an extruded loop containing three "proximal" Cys ligands of the iron-sulfur cluster. === High potential iron-sulfur proteins === High potential iron-sulfur proteins (HiPIPs) form a unique family of Fe<sub>4</sub>S<sub>4</sub> ferredoxins that function in anaerobic electron transport chains. Some HiPIPs have a redox potential higher than any other known iron-sulfur protein (e.g., HiPIP from ''Rhodopila globiformis'' has a redox potential of ca. 450 mV). Several HiPIPs have so far been characterized structurally, their folds belonging to the α+β class. As in other bacterial ferredoxins, the [Fe<sub>4</sub>S<sub>4</sub>] cluster adopts a cubane-like conformation and is ligated to the protein ''via'' four Cys residues. ==References== * {{cite journal | author=Bruschi, M. and Guerlesquin, F. | title=Structure, function and evolution of bacterial ferredoxins | journal=FEMS Microbiol. Rev. | year=1988 | volume=4 | pages=155&ndash;175 | pmid=3078742}} * {{cite journal | author=Ciurli, S. and Musiani, F. | title=High potential iron-sulfur proteins and their role as soluble electron carriers in bacterial photosynthesis: tale of a discovery | journal=Photosynth. Res. | year=2005 | volume=85 | pages=115&ndash;131 | pmid=15977063 | doi=10.1007/s11120-004-6556-4}} * {{cite journal | author=Fukuyama, K. | title=Structure and function of plant-type ferredoxins | journal=Photosynth. Res. | year=2004 | volume=81 | pages=289&ndash;301 | pmid=16034533 | doi=10.1023/B:PRES.0000036882.19322.0a}} * {{cite journal | author=Grinberg, A.V., Hannemann, F., Schiffler, B., Müller, J., Heinemann, U. and Bernhardt, R. | title=Adrenodoxin: structure, stability, and electron transfer properties | journal=Proteins | year=2000 | volume=40 | pages=590&ndash;612 | pmid=10899784 | doi=10.1002/1097-0134(20000901)40:4<590::AID-PROT50>3.0.CO;2-P}} * {{cite journal | author=Holden,H.M., Jacobson, B.L., Hurley, J.K., Tollin, G., Oh, B.H., Skjeldal, L., Chae, Y.K., Cheng, H., Xia, B. and Markley, J.L. | title=Structure-function studies of [2Fe-2S] ferredoxins | journal=J. Bioenerg. Biomembr. | year=1994 | volume=26 | pages=67&ndash;88 | pmid=8027024 | doi=10.1007/BF00763220}} * {{cite journal | author=Meyer, J. | title=Ferredoxins of the third kind | journal=FEBS Lett. | year=2001 | volume=509 | pages=1&ndash;5 | pmid=11734195 | doi=10.1016/S0014-5793(01)03049-6}} * {{cite journal | author=Mortenson, L.E., Valentine, R.C. and Carnahan, J.E. | title=An electron transport factor from ''Clostridium pasteurianum'' | journal=Biochem. Biophys. Res. Commun. | year=1962 | volume=7 | pages=448&ndash;452 | pmid=14476372 | doi=10.1016/0006-291X(62)90333-9}} * {{cite journal | author=Tagawa, K. and Arnon, D.I. | title=Ferredoxins as electron carriers in photosynthesis and in the biological production and consumption of hydrogen gas | journal=Nature | year=1962 | volume=195 | pages=537&ndash;543 | pmid=14039612 | doi=10.1038/195537a0}} * {{cite journal | author=Valentine, R.C. | title=Bacterial ferredoxin | journal=Bacteriol Rev. | year=1964 | volume=28 | pages=497&ndash;517 | pmid=14244728}} ==External links== * {{InterPro|IPR006057}} - 2Fe-2S ferredoxin subdomain * {{InterPro|IPR001055}} - Adrenodoxin * {{InterPro|IPR001450}} - 4Fe-4S ferredoxin, iron-sulfur binding * {{InterPro|IPR000170}} - High potential iron-sulfur protein * {{PDB|1F37}} - X-ray structure of thioredoxin-like ferredoxin from ''Aquifex aeolicus'' (''Aa''Fd) [[Category:Iron-sulfur proteins]] [[Category:Photosynthesis]] [[de:Ferredoxin]] [[ja:フェレドキシン]] [[pl:Ferredoksyna]] [[pt:Ferredoxina]]