Binding of the metalloregulatory protein DtxR to the diphtheria tox operator requires a divalent heavy metal ion and protects the palindromic sequence from DNase I digestion.
Transcription of the corynebacteriophage diphtheria tox operon has been shown to be regulated through a corynebacterial determined factor DtxR. The dtxR gene has been recently cloned and expressed in Escherichia coli, and shown to regulate the expression of beta-galactosidase expression from a diphtheria tox promoter/operator-lacZ transcriptional fusion. Tao et al. (Tao, X., Boyd, J., and Murphy, J. R. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 5897-5901) have recently shown by gel mobility shift assay that the binding of DtxR to the tox operator requires a divalent heavy metal ion, as well as the 27-base pair interrupted palindromic sequence. We now show the activation of DtxR in the presence of Co2+, Fe2+, or Mn2+ results in the protection of a 33- and 27-nucleotide region on the coding and non-coding strand from DNase I digestion, respectively. DtxR is also activated in the presence of Ni2+; however, this metalloregulatory factor is only weakly activated by Zn2+. The diphtheria tox regulatory region protected from DNase I digestion in the presence of activated DtxR encompasses the 27-base pair interrupted palindromic sequence.
Tao
X
X
Evans Department of Clinical Research, University Hospital, Boston, Massachusetts 02118.
Murphy
J R
JR
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002413:Cations, Divalent; D003353:Corynebacterium diphtheriae / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism*; D004167:Diphtheria Toxin / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial; D008670:Metals / Q000378:metabolism*; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D010957:Plasmids; D011994:Recombinant Proteins / Q000235:genetics
D001426:Bacterial Proteins; D002413:Cations, Divalent; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D004167:Diphtheria Toxin; C075586:DtxR protein, Corynebacterium diphtheriae; D008670:Metals; D011994:Recombinant Proteins; D003850:Deoxyribonuclease I