Publication Abstract from PubMed
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.
Mechanism of metal ion activation of the diphtheria toxin repressor DtxR.,D'Aquino JA, Tetenbaum-Novatt J, White A, Berkovitch F, Ringe D Proc Natl Acad Sci U S A. 2005 Dec 20;102(51):18408-13. Epub 2005 Dec 13. PMID:16352732[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
