This family includes the Diphtheria toxin repressor [1]. It acts as an iron-binding repressor of diphtheria toxin gene expression and may serve as a global regulator of gene expression. DTXR comprises an N-terminal DNA-binding domain, an interface domain (which contains two metal-binding sites) and a third, very flexible C-terminal domain. The second domain is responsible for dimerization and metal binding. Binding of DTXR to Tox operator requires a divalent metal ion such as cobalt, ferric, manganese and nickel whereas zinc shows weak activation [2]. This domain can also bind Cd(II), Ca(II) and Cu(II) (Matilla et. al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).

1: Structures of the apo- and the metal ion-activated forms of the diphtheria tox repressor from Corynebacterium diphtheriae. Schiering N, Tao X, Zeng H, Murphy JR, Petsko GA, Ringe D; Proc Natl Acad Sci USA 1995;92:9843-9850. PMID:7568230

2: Three-dimensional structure of the diphtheria toxin repressor in complex with divalent cation co-repressors. Qiu X, Verlinde CL, Zhang S, Schmitt MP, Holmes RK, Hol WG; Structure 1995;3:87-100. PMID:7743135