IscU_like and NifU_like proteins. IscU and NifU function as a scaffold for the assembly of [2Fe-2S] clusters before they are transferred to apo target proteins. They are highly conserved and play vital roles in the ISC and NIF systems of Fe-S protein maturation. NIF genes participate in nitrogen fixation in several isolated bacterial species. The NifU domain, however, is also found in bacteria that do not fix nitrogen, so it may have wider significance in the cell. Human IscU interacts with frataxin, the Friedreich ataxia gene product, and incorrectly spliced IscU has been shown to disrupt iron homeostasis in skeletal muscle and cause myopathy.