This family of proteins is likely to be involved in the assembly of iron-sulphur clusters. It may function as an adaptor protein. In Escherichia coli Swiss:P0C0L9 forms part of the isc operon, which encodes genes involved in iron-sulphur cluster assembly. Its structure is entirely alpha helical, and it contains a modified wing-helix structure, usually found in DNA-binding proteins. It binds to Fe2+ and Fe3+ ions and to the cysteine desulfurase IscS, the same surface of the protein is involved in both binding to iron and to IscS [1,2].

1: YfhJ, a molecular adaptor in iron-sulfur cluster formation or a frataxin-like protein?. Pastore C, Adinolfi S, Huynen MA, Rybin V, Martin S, Mayer M, Bukau B, Pastore A; Structure. 2006;14:857-867. PMID:16698547

2: Structural basis for Fe-S cluster assembly and tRNA thiolation mediated by IscS protein-protein interactions. Shi R, Proteau A, Villarroya M, Moukadiri I, Zhang L, Trempe JF, Matte A, Armengod ME, Cygler M; PLoS Biol. 2010;8:e1000354. PMID:20404999