Download MendeleyMechanism of metal ion activation of the diphtheria toxin repressor DtxR.
D'Aquino, J.A., Tetenbaum-Novatt, J., White, A., Berkovitch, F., Ringe, D.(2005) Proc Natl Acad Sci U S A 102: 18408-18413
- PubMed: 16352732
- DOI: https://doi.org/10.1073/pnas.0500908102
- Primary Citation of Related Structures:
1XCV - PubMed Abstract:
The diphtheria toxin repressor (DtxR) is a metal ion-activated transcriptional regulator that has been linked to the virulence of Corynebacterium diphtheriae. Structure determination has shown that there are two metal ion binding sites per repressor monomer, and site-directed mutagenesis has demonstrated that binding site 2 (primary) is essential for recognition of the target DNA repressor, leaving the role of binding site 1 (ancillary) unclear. Calorimetric techniques have demonstrated that although binding site 1 (ancillary) has high affinity for metal ion with a binding constant of 2 x 10(-7), binding site 2 (primary) is a low-affinity binding site with a binding constant of 6.3 x 10(-4). These two binding sites act in an independent fashion, and their contribution can be easily dissected by traditional mutational analysis. Our results clearly demonstrate that binding site 1 (ancillary) is the first one to be occupied during metal ion activation, playing a critical role in stabilization of the repressor. In addition, structural data obtained for the mutants Ni-DtxR(H79A,C102D), reported here, and the previously reported DtxR(H79A) have allowed us to propose a mechanism of metal activation for DtxR.
Organizational Affiliation:
Department of Chemistry, Brandeis University, Waltham, MA 02454, USA.
