Iron-sulfur cluster
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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 know 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.[1][1][1]
Synthetic analogues
Synthetic analogues of the naturally occuring Fe-S clusters were first reported by Holm and coworkers.[1] Treatment of iron salts with a mixture of thiolates and sulfide affords derivatives such as (Et4N)2Fe4S4(SCH2Ph)4].
References
See also
External link
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
