Iron-sulfur cluster

Iron -sulfur cluster (Fe -S- centers) are multi- complexes of iron and sulfur to the size of clusters that are involved as co-factors for the enzyme reactions. The most common and most stable are ( 4Fe- 4S) and ( 2Fe- 2S). In general the cluster can be destroyed if they are accessible to free oxygen. Accessibility is the protection of the binding enzyme -dependent.

This Fe-S enzymes act in the centers as Elektronentransferreaktanden, Lewis acids and free-radical generators. For example, nitrogen, ammonia, hydrogen, are converted into protons and carbon monoxide into carbon dioxide:

The iron atoms of the centers are coordinated by an inorganic sulphide and the side chains of amino acids. Cysteines can coordinate for example, via their thiol group (see figure).

Biosynthesis

Already under reducing, aqueous conditions form spontaneously rhombic ( 2Fe- 2S)- complexes. Other metal ions, such as nickel or molybdenum may be added to the complex in order. This is done in the organism especially effective participation of a protein complex containing the iron-sulfur cluster protein scaffold ( ISCU ).

ISCU thereby takes over the role of the binding of the iron atoms, which are transported from ISCA zoom, while the enzyme cysteine ​​desulfurase provide under Cysteinverbrauch sulfur atoms. First ( 2Fe- 2S) is assembled, which is finally obtained by dimerization ( 4Fe- 4S). This process can take place in both the mitochondria and the cytosol, after which the finished ( 4Fe- 4S) transported to the plasma is equal to or incorporated into available enzymes.

Occurrence

Anaerobic bacteria and archaea living partly also contain oxygen-sensitive enzymes with a nickel -, iron-and sulfur- center, which is called cluster C.

The enzyme nitrogenase contains an Fe - Mo-S cluster as a cofactor.

Iron - sulfur clusters are found in mitochondria, hydrogenosomes and Mitosomen.

List of human proteins ( 2Fe- 2S)

• NADH dehydrogenase, succinate dehydrogenase and cytochrome c reductase ( complex I, II and III of the respiratory chain, the citric acid cycle )
• Adrenodoxin ( synthesis of thyroid hormones )
• Xanthine oxidase ( nucleotide metabolism )
• Aldehyde oxidase ( biotransformation, elimination of nicotine)
• Ferrochelatase ( Porphyrinmetabolismus )
• Miner1 and Miner2

List of human proteins ( 4Fe- 4S)

• NADH dehydrogenase and succinate dehydrogenase ( complex I and II of the respiratory chain, Krebs cycle )
• Aconitase ( citric acid cycle )
• Amidophosphoribosyltransferase ( purine, inosine monophosphate de novo synthesis)
• Dihydropyrimidine dehydrogenase ( amino acid synthesis, the synthesis of β -alanine )
• IREBP2 ( iron metabolism )
• Lipoylsynthase (protein modification)
• Nuclear enzymes DNA primase and endonuclease III -like