Nature Structural Biology
3, 382 - 387 (1996)
doi:10.1038/nsb0496-382
Identification of the primary metal ion-activation sites of the diphtheria tox represser by X-ray crystallography and site-directed mutational analysisX. Ding1, H. Zeng2, N. Schiering2, 3, D. Ringe1
& J.R. Murphy1
1Departments of Biochemistry and Chemistry, and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02154 USA
2Evans Department of Clinical Research and the Department of Medicine, Boston University Medical Center Hospital, Boston, Massachusetts 02118 USA
3Present address: Pharmacia and Upjohn, via Giovanni XXIII, 2320014 Nerviano[MI], Italy The diphtheria tox represser, DtxR, is a 226 amino acid transition metal ion-activated regulatory protein that controls the expression of diphtheria toxin in toxigenic Corynebacterium diphtheriae. The previously solved three-dimensional DtxR structures have identified two potential metal ion binding sites which may play a role in the activation of DNA binding by the represser. We have used both X-ray crystallographic and site-directed mutational analysis of DtxR(C102D)−Ni2+ complexes and DtxR to identify the metal ion-binding site which results in the activation of the repressor. We demonstrate that DtxR contains both a primary and an ancillary metal ion binding site. The primary site functions directly in the activation of DNA binding. In contrast, the ancillary site contributes weakly, if at all, to activation.
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