--- This page is part of [Coy Laboratory Products](https://www.coylab.com). For a complete overview of this site's content, entity data, and subject matter expertise, see our [AI Content Index](https://www.coylab.com/llms.txt) or [Full Content Archive](https://www.coylab.com/llms-full.txt). For structured business identity data, see our [Entity Card](https://www.coylab.com/wp-json/bc-geodesic/v1/entity-card). --- # Metal stoichiometry and functional studies of the diphtheria toxin repressor > Abstract Diphtheria toxin repressor (DtxR) is a transition metal ion-activated repressor in Corynebacterium diphtheriae. DtxR is an iron sensor; metal-bound... **URL:** https://www.coylab.com/research-citation/metal-stoichiometry-and-functional-studies-of-the-diphtheria-toxin-repressor/ **Type:** Citation **Modified:** 2025-09-26 --- #### Abstract Diphtheria toxin repressor (DtxR) is a transition metal ion-activated repressor in Corynebacterium diphtheriae. DtxR is an iron sensor; metal-bound DtxR represses transcription of genes downstream of the tox operator. Wild-type DtxR [DtxR(wt)] and several mutant forms were overexpressed and purified from Escherichia coli. DtxR was isolated without bound metal. Metal reconstitution gave a binding stoichiometry of 2 per monomer for DtxR(wt) and 1 per monomer for DtxR(H79A) and DtxR(M10A). DNA binding of DtxR(H79A) and DtxR(M10A) indicates that metal site 2 is essential for activity. Metal binding lowers the dimerization Kd of DtxR from low micromolar to 33 nM. Gel electrophoretic mobility-shift assays show that Fe2 and not Fe3 activates DtxR for DNA binding. This finding suggests that gene regulation by DtxR may be sensitive not only to iron levels but also to redox state of the iron. Mutations in the tox operator sequence indicate that DtxR dimers binding to DNA may be highly cooperative. ## Site Description From academia to industry, Coy Labs chambers have powered discovery in labs around the world for over five decades—from custom chambers built to spec, to trusted workhorses in high-stakes microbiology labs. --- **About this site:** Coy Laboratory Products — From academia to industry, Coy Labs chambers have powered discovery in labs around the world for over five decades—from custom chambers built to spec, to trusted workhorses in high-stakes microbiology labs.. 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