+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Characterization of a defective diphtheria toxin repressor (dtxR) allele and analysis of dtxR transcription in wild-type and mutant strains of Corynebacterium diphtheriae



Characterization of a defective diphtheria toxin repressor (dtxR) allele and analysis of dtxR transcription in wild-type and mutant strains of Corynebacterium diphtheriae



Infection and Immunity 59(11): 3903-3908



The production of diphtheria toxin and siderophore by the Corynebacterium diphtheriae regulatory mutant C7(beta)hm723 is resistant to the inhibitory effects of iron, and the mutant strain is defective for function of the regulatory gene dtxR. A 2.8-kb HindIII fragment carrying the C7(beta)hm723 dtxR allele was cloned and characterized in Escherichia coli. The restriction endonuclease maps of the 2.8-kb HindIII fragment from C7(beta)hm723 and the corresponding fragment from wild-type C. diphtheriae C7 were identical. RNA dot blot analysis with total RNA isolated from wild-type C. diphtheriae C7 and C7(beta)hm723 indicated that the dtxR gene was transcribed at very low but equivalent levels in both strains and was not regulated by iron. beta-Galactosidase synthesis from a tox-lacZ translational fusion construct in E. coli in high-iron medium was not repressed by the C7(beta)hm723dtxR allele, but was strongly repressed by the wild-type dtxR gene. The 28- to 29-kDa polypeptide expressed from the mutant dtxR allele in E. coli had the same electrophoretic mobility as the wild-type dtxR gene product in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The nucleotide sequence of the coding region and the 5' upstream region of the C7(beta)hm723 dtxR allele was determined and compared with the wild-type nucleotide sequence. The dtxR allele from C7(beta)hm723 contained a single-base change located 140 nucleotides from the 5' start of the gene, which resulted in replacement of arginine in the wild-type sequence by histidine in the mutant protein. These data demonstrate that C7(beta)hm723 expresses a mutant DtxR repressor protein that is severely defective in repressor activity.

Please choose payment method:






(PDF emailed within 1 workday: $29.90)

Accession: 039519420

Download citation: RISBibTeXText

PMID: 1718867


Related references

Iron dependent regulation of diphtheria toxin and siderophore expression by the cloned corynebacterium diphtheriae repressor gene dtxr in corynebacterium diphtheriae c7 strains. Infection & Immunity 59(6): 1899-1904, 1991

Iron dependent regulation of diphtheria toxin and siderophore expression by the cloned corynebacterium diphtheriae repressor gene dtxr in strains of corynebacterium diphtheriae c7. Abstracts of the General Meeting of the American Society for Microbiology 91: 27, 1991

Molecular characterization of diphtheria toxin repressor (dtxR) genes present in nontoxigenic Corynebacterium diphtheriae strains isolated in the United Kingdom. Journal of Clinical Microbiology 43(1): 223-228, 2005

Iron-dependent regulation of diphtheria toxin and siderophore expression by the cloned Corynebacterium diphtheriae repressor gene dtxR in C. diphtheriae C7 strains. Infection and Immunity 59(6): 1899-1904, 1991

Characterization of lipoprotein IRP1 from Corynebacterium diphtheriae, which is regulated by the diphtheria toxin repressor (DtxR) and iron. Infection and Immunity 65(12): 5364-5367, 1997

Identification and characterization of three new promoter/operators from Corynebacterium diphtheriae that are regulated by the diphtheria toxin repressor (DtxR) and iron. Infection and Immunity 65(10): 4273-4280, 1997

Point mutations in tox promoter/operator and diphtheria toxin repressor (DTXR) gene associated with the level of toxin production by Corynebacterium diphtheriae strains isolated in Belarus. Molekuliarnaia Genetika Mikrobiologiia i Virusologiia 2007(1): 22-29, 2007

Construction and characterization of transposon insertion mutations in Corynebacterium diphtheriae that affect expression of the diphtheria toxin repressor (DtxR). Journal of Bacteriology 184(20): 5723-5732, 2002

Cloning, sequence, and footprint analysis of two promoter/operators from Corynebacterium diphtheriae that are regulated by the diphtheria toxin repressor (DtxR) and iron. Journal of Bacteriology 176(4): 1141-1149, 1994

Characterization of an iron-dependent regulatory protein (IdeR) of Mycobacterium tuberculosis as a functional homolog of the diphtheria toxin repressor (DtxR) from Corynebacterium diphtheriae. Infection and Immunity 63(11): 4284-4289, 1995

Genetic and biophysical studies of diphtheria toxin repressor (DtxR) and the hyperactive mutant DtxR(E175K) support a multistep model of activation. Proceedings of the National Academy of Sciences of the United States of America 101(8): 2506-2511, 2004

Prediction of DtxR regulon: identification of binding sites and operons controlled by Diphtheria toxin repressor in Corynebacterium diphtheriae. Bmc Microbiology 4: 38-38, 2004

Heterogeneity of diphtheria toxin gene, tox, and its regulatory element, dtxR, in Corynebacterium diphtheriae strains causing epidemic diphtheria in Russia and Ukraine. Journal of Clinical Microbiology 34(7): 1711-1716, 1996

Motion of the DNA-binding domain with respect to the core of the diphtheria toxin repressor (DtxR) revealed in the crystal structures of apo- and holo-DtxR. Journal of Biological Chemistry 273(35): 22420-7, 1998

DtxR-tox operator interactions and analysis of a mutant DtxR repressor with decreased binding to divalent metals. Abstracts of the General Meeting of the American Society for Microbiology 93: 212, 1993