These findings indicate that transcription of iutE is controlled by a complex mechanism that involves multiple regulatory factors whose activity is impacted by both Zn and Fe. Analysis of the iutE promoter region identified a 50-bp sequence at the 3′ end of the iutD gene that is required for the DtxR-dependent and iron-responsive activation of the iutE gene. Electrophoretic mobility shift assays showed that DtxR does not bind to the iutE upstream region, which indicates that DtxR regulation of iutE is indirect and that other regulatory factors controlled by DtxR are likely responsible for the iron-responsive regulation. Transcription of iutE was positively regulated in response to iron availability in a DtxR-dependent manner and was repressed in response to Zn by the Zn-dependent repressor Zur. We demonstrated that the iutABCD genes are cotranscribed and repressed in response to iron by the iron-responsive repressor DtxR. We showed that IutA and IutE are both membrane proteins with comparable Mn and Zn binding abilities. In this study, we identified a genetic region that encodes an ABC-type transporter ( iutBCD) and that is flanked by two genes ( iutA and iutE) encoding putative substrate binding proteins of the cluster 9 family, a related group of transporters associated primarily with the import of Mn and Zn. diphtheriae, systems involved in the acquisition of other metals such as zinc and manganese remain poorly characterized. While mechanisms required for heme iron acquisition are well known in C. Corynebacterium diphtheriae, a Gram-positive, aerobic bacterium, is the causative agent of diphtheria and cutaneous infections.