EisenSchwefelCluster

EisenSchwefelCluster, usually called an iron-sulfur cluster, denotes a class of inorganic cofactors built from iron ions bridged by sulfide ligands and embedded in proteins. These clusters are widespread in biological systems and play essential roles in electron transfer, redox chemistry, and catalysis. The most common cores are [2Fe-2S], [3Fe-4S], and [4Fe-4S], each of which can participate in multiple oxidation states and be stabilized by cysteine thiolate ligands from the surrounding protein.

Structural features: Iron-sulfur clusters typically feature iron centers coordinated by cysteine residues, sometimes histidines, with inorganic sulfide bridges linking iron atoms. The clusters can be cubane-shaped ([4Fe-4S]) or more open architectures ([2Fe-2S], [3Fe-4S]). Their electronic properties enable fast, reversible electron transfer, with redox potentials varying over a wide range depending on core type and protein environment.

Biogenesis and protection: In bacteria and mitochondria, dedicated assembly pathways (Isc, Suf, Nif systems) build and insert clusters into apoproteins. Maturation factors and chaperones assist repair and trafficking. Iron-sulfur clusters are highly oxygen-sensitive, and cellular mechanisms minimize exposure to reactive oxygen species to preserve function.

Function and significance: Iron-sulfur clusters occur in ferredoxins, hydrogenases, nitrogenase components, and several oxidoreductases, supporting energy metabolism, nitrogen fixation, and photosynthesis. They are considered among the most ancient cofactors, illustrating the evolution of redox chemistry in biology, and they remain a focus of bioinorganic chemistry and bioengineering for synthetic catalysts and sustainable technologies.