Most members of this family are small (approximately 36 amino acids) proteins that from homodimeric complexes. Each subunit contains a high-spin iron atom tetrahedrally bound to four cysteinyl sulphur atoms This family has a similar fold to the rubredoxin metal binding domain [1]. It is also found as the N-terminal domain of desulfoferrodoxin, see (Pfam:PF01880).

1: Structural studies by X-ray diffraction on metal substituted desulforedoxin, a rubredoxin-type protein. Archer M, Carvalho AL, Teixeira S, Moura I, Moura JJ, Rusnak F, Romao MJ; Protein Sci 1999;8:1536-1545. PMID:10422844