Required for nuclear and mitochondrial iron-sulfur protein biosynthesis. Cofactor biosynthesis; iron-sulfur cluster biosynthesis. Interacts with FXN. Interaction is increased by nickel. Interaction is inhibited by calcium, magnesium, manganese, copper, cobalt, zinc, and iron. Forms a complex with the cytosolic/nuclear form of NFS1. The complex increased the stability of NFS1. Belongs to the complex I LYR family.