Fe—S clusters as electron carriers

Mono(p-oxo) complexes, osmium, 37 311 Monooxygenases, Fe—S clusters as electron carriers, 38 305... 

Fe—S clusters as electron carriers, 38 307 inactive, oxidized form, 40 343 spectroscopy, 40 343-344 ions... 

A second group of electron carriers in mitochondrial membranes are the iron-sulfur [Fe-S] clusters which are also bound to proteins. Iron-sulfur proteins release Fe3+ or Fe2+ plus H2S when acidified. The "inorganic clusters" bound into the proteins have characteristic compositions such as Fe2S2 and Fe4S4. The sulfur atoms of the clusters can be regarded as sulfide ions bound to the iron ions. The iron atoms are also attached to other sulfur atoms from cysteine side chains from the proteins. The Fe-S proteins are often tightly associated with other components of the electron transport chain. For example, the flavoproteins Flavin 1, Flavin 2, and Flavin 3 shown in Fig. 10-5 all contain Fe-S clusters as does the Q-cytochrome b complex. All of these Fe-S clusters seem to be one-electron carriers. 

H, C, N, O, P, S The elements H, C, N and O make the best polymers such as proteins, with high kinetic stability. The elements P in phosphate esters or anhydrides and S in thiols or thioethers increase the reactivity of small molecules and polymers. Clusters of S with Fe or Cu are important electron carrier systems. 

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