The diphtheria toxin repressor protein (DTXR) is a member of this group [<cite idref="PUB00004874"/>]. In <taxon tax_id="1717">Corynebacterium diphtheriae</taxon> where it has been studied in some detail this protein actsas an iron-binding repressor of dipheteria toxin gene expression and may serve as a global regulator of gene expression. The N terminus may be involved in iron binding andmay associate with the Tox operator. Binding of DTXR to Tox operator requires a divalentmetal ion such as cobalt, ferric, manganese and nickel whereas zinc shows weak activation [<cite idref="PUB00005267"/>]. Iron dependent repressor