In the context of the plethora of proteins harboring iron-sulfur clusters we have already reviewed structure/electrochemistry of metalloproteins expressing single types of iron-sulfur clusters (namely: {Fe(Cys)(4)}, {[Fe2S2](Cys)(4)}, {[Fe2S2](Cys)(3)(X)} (X = Asp, Arg, His), {[Fe2S2](Cys)(2)(His)(2)}, {[Fe3S4](Cys)(3)}, {[Fe4S4](Cys)(4)} and {[Fe4S4](S-Cys(gamma))(3)(nonthiolate ligand)} cores) and their synthetic analogs. More recently we are focussing on structure/electrochemistry of metalloproteins harboring iron-sulfur centres of different nuclearities. Having started such a subject with proteins harboring [4Fe-4S] and [2Fe-2S] clusters, we now depict the state of art of proteins containing [4Fe-4S] and [3Fe-4S] clusters.