Iron-sulfur cluster assembly enzyme （ISCU） belongs to the nifU family. Iron-sulfur （Fe-S） clusters are required for several mitochondrial enzymes and other subcellular compartment proteins. ISCU interacts with ISCS （a cysteine desulfurase） to sequester inorganic sulfur for Fe-S cluster assembly. The ISCU-ISCS protein complex localizes in both mitochondria and cytosol， implying that Fe-S cluster assembly occurs in multiple subcellular compartments in mammalian cells.
