Iron sulfur clusters assembly model

This section is organized as follows we first start with a discussion of the electrochemical behavior of the Roussin-type synthetic iron- sulfur clusters for their historic importance and as an interesting introduction to poly iron-sulfur centers redox chemistry. Then we review iron-sulfur centers in proteins and artificial models in the order of increasing iron content. Finally, biological iron-sulfur centers and artificial models directly linked to other inorganic centers, the so-called bridged molecular assemblies, are considered. 

While most soluble cellular iron is associated with an ill-defined labile iron pool, much of the iron that is used by the cell is found in the form of specific iron cofactors especially as iron-sulfur clusters and hemes. The biosynthesis of iron-sulfur centers has only come of age within the past decade following the characterization of operons encoding cluster assembly genes by Dean and coworkers 4), In eukaryotes, homologous proteins are nuclear transcribed. While predominantly localized within the mitochondrial matrix, one group has reported cytosolic ISU (cluster assembly protein) and NFS (S-donor protein) in human cell lines (5). Alternative cytoplasmic cluster maturation proteins have also been proposed (6). Whether the cytosolic components represent an independent assembly apparatus is unclear, nevertheless, both models support a role for ISU-mediated assembly of [2Fe-2S] building blocks prior to delivery to a target protein (7-P). 

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