Iron-sulfur proteins with other prosthetic groups

More complex iron-sulfur proteins have been described in the literature, where the iron-sulfur center is associated with other prosthetic groups such as flavin, heme, molybdenum, thiamine diphosphate (TDP), selenium and chlorophyll. 

Table 3 describes the basic iron-sulfur structures and the oxidation states that can be found in simple proteins and how they may associate with other prosthetic groups. 

Iron-sulfur clusters (7) occur as prosthetic groups in oxidoreductases, but they are also found in lyases—e.g., aconitase (see p. 136) and other enzymes. Iron-sulfur clusters consist of 2-4 iron ions that are coordinated with cysteine residues of the protein (-SR) and with anorganic sulfide ions (S). Structures of this type are only stable in the interior of proteins. Depending on the number of iron and sulfide ions, distinctions are made between [Fe2S2], [Fe3S4], and [Fe4S4] clusters. These structures are particularly numerous in the respiratory chain (see p. 140), and they are found in all complexes except complex IV. 

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