iron-sulfur cluster

Information about iron-sulfur cluster

An iron-sulfur cluster is a structural motif found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase and Coenzyme Q - cytochrome c reductase, and nitrogenase. Usually the term iron-sulfur cluster refers species within Iron-sulfur proteins that contain only iron and sulfur, and three distinct kinds are well known:[1]
  • The 2 iron, 2 sulfur cluster, consisting of two iron atoms, with two inorganic sulfur atoms found between the irons and acting as bridging ligands. The irons themselves are usually coordinated to the sulfurs of 4 cysteine side chains. In the related Rieske proteins, a pair of cysteinyl residues on one iron center are replaced by 2 imidazole ligands from the side chain of two histidine residues. These species exist in two oxidation states, (FeIII)2 and FeIIIFeII.
  • The 4 iron, 4 sulfur cluster, consisting of 4 irons, with 4 inorganic sulfur atoms found between the irons and acting as bridging ligands. The irons, once again, are coordinated to the protein via the sulfurs of 4 cysteine side chains. These species exist in two oxidation states, (FeIII)2(FeII)2 and either (FeIII)3(FeII)1 or (FeIII)1(FeII)3.
  • The 3 iron, 4 sulfur cluster, which is a 4 iron, 4 sulfur cluster with one missing iron atom.

Function

Iron-sulfur clusters are best known for their role in oxidation-reduction reactions. They have many other functions including catalysis as illustrated by aconitase, generation of radicals as illustrated by SAM-dependent enzymes, and as sulfur donors in the biosynthesis of lipoic acid and biotin. Additionally some Fe-S proteins regulate gene expression. Fe-S proteins are vulnerable to attack by biogenic nitric oxide.

Biosynthesis

The biosynthesis of the Fe-S clusters has been well studied.[2][3][4]

Synthetic analogues

Synthetic analogues of the naturally occurring Fe-S clusters were first reported by Holm and coworkers.[5] Treatment of iron salts with a mixture of thiolates and sulfide affords derivatives such as (Et4N)2Fe4S4(SCH2Ph)4].

References

1. ^ S. J. Lippard, J. M. Berg “Principles of Bioinorganic Chemistry” University Science Books: Mill Valley, CA; 1994. ISBN 0-935702-73-3.
2. ^ Johnson D, Dean DR, Smith AD, Johnson MK. Structure, function and formation of biological iron–sulfur clusters. Annu Rev Biochem. 2005;74:247–281.
3. ^ Johnson, M.K. and Smith, A.D. (2005) Iron–sulfur proteins in: Encyclopedia of Inorganic Chemistry (King, R.B., Ed.), 2nd edn, John Wiley & Sons, Chichester.
4. ^ Lill R, Mühlenho U. Iron–sulfur-protein biogenesis in eukaryotes. Trends Biochem Sci. 2005;30:133–141.
5. ^ Herskovitz, t.; Averill, B. A.; Holm, R. H.; Ibers, J. A.; Phillips, W. D. and Weiher, J. F., "Structure and properties of a synthetic analog of bacterial iron-sulfur proteins", Proc. Nat. Acad. Sci. U. S. A., 1972, 69, 2437-41

See also

External links

structural motif is a three-dimensional structural element or fold within the chain, which appears also in a variety of other molecules. In the context of proteins, the term is sometimes used interchangeably with "structural domain," although a domain need not be a motif
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In biochemistry, a metalloprotein is a generic term for a protein that contains a metal cofactor. The metal may be an isolated ion or may be coordinated with a nonprotein organic compound, such as the porphyrin found in hemoproteins.
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Ferredoxins (from Latin ferrum: iron + redox, often abbreviated "fd") are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions.

Overview

The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co.
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NADH dehydrogenase (EC 1.6.5.3 ) is an enzyme located in the inner mitochodrial membrane that catalyzes the transfer of electrons from NADH to coenzyme Q (CoQ). It is also called the NADH:quinone oxidoreductase.
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The coenzyme Q : cytochrome c — oxidoreductase, sometimes called the cytochrome bc1 complex, and at other times complex III, is the third complex in the electron transport chain (EC 1.10.2.
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Nitrogenase (EC 1.18.6.1 ) is the enzyme used by some organisms to fix atmospheric nitrogen gas (N2). It is the only known family of enzymes which accomplishes this process.
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Iron-sulfur proteins are proteins characterized by the presence of polymetallic systems (iron-sulfur clusters) containing sulfide ions, in which the iron ions have variable oxidation states.
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3, 4, 6
(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol−1
2nd: 1561.9 kJmol−1
3rd: 2957 kJmol−1

Atomic radius 140 pm
Atomic radius (calc.
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6
(strongly acidic oxide)
Electronegativity 2.58 (Pauling scale)
Ionization energies
(more) 1st: 999.6 kJmol−1
2nd: 2252 kJmol−1
3rd: 3357 kJmol−1

Atomic radius 100 pm
Atomic radius (calc.
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ligand (latin ligare = to bind) is a molecule that is able to bind to and form a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is an effector molecule binding to a site on a target protein, by intermolecular forces such as ionic bonds,
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Cysteine (abbreviated as Cys or C)[1] is an α-amino acid with the chemical formula HO2CCH(NH2)CH2SH. It is not an essential amino acid, which means that humans can synthesize it. Its codons are UGU and UGC.
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side chain in organic chemistry and biochemistry is a part of a molecule that is attached to a core structure. An R group is a generic label for a side chain which can be anything; however, it is typically stable and covalently linked to the adjoining atom.
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Rieske proteins include ISP components of cytochrome b6f complex), aromatic-ring-hydroxylating dioxygenases (phthalate dioxygenase, benzene, napthalene and toluene 1,2-dioxygenases) and arsenite oxidase (EC 1.20.98.1 ).
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Imidazole is a heterocyclic aromatic organic compound. It is further classified as an alkaloid. Imidazole refers to the parent compound C3H4N2, whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents.
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Histidine (abbreviated as His or H)[1] is one of the 20 most common natural amino acids present in proteins. In the nutritional sense, in humans, histidine is considered an essential amino acid, but mostly only in children.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the
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Identifiers
Symbol ACO2

Entrez 50
HUGO 118
OMIM 100850

RefSeq NM_001098
UniProt Q99798
Other data
EC number 4.2.1.3
Locus Chr. 22 q13.2 Aconitase (aconitate hydratase; EC 4.2.1.
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S-adenosyl methionine (SAM) is a cofactor involved in methyl group transfers. SAM was first discovered in 1952.[1] It is made from adenosine triphosphate (ATP) and methionine by methionine adenosyltransferase EC 2.5.1.6 .
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Lipoic acid is the organic compound, one enantiomer of which is an essential cofactor for many enzyme complexes. The molecule consists of a carboxylic acid and a cyclic disulfide. Only the R-enantiomer is biologically significant.
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Biotin, also known as vitamin H or B 7 , has the chemical formula C10H16N2O3S (Biotin; Coenzyme R, Biopeiderm), is a water-soluble B-complex vitamin which is composed of an ureido (tetrahydroimidizalone) ring fused with a
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Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of mammals including humans and is an extremely important intermediate in the chemical industry.
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Tetraethylammonium (TEA) is a potassium-selective ion channel blocker. It is used in neurophysiology experiments to block the voltage activated potassium channels involved in the trailing part of the transmission of an action potential along a neuron.
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Bioinorganic chemistry is a specialized field that spans the chemistry of metal-containing molecules within biological systems. This field is concerned with the control and use of metal ions in biochemical processes.
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