title: DNA sequences and characterization of dtxR alleles from Corynebacterium diphtheriae PW8(-), 1030(-), and C7hm723(-).
abstract: The structural gene encoding DtxR, an iron-dependent diphtheria tox regulatory element, has recently been cloned and sequenced from the C7(-) strain of Corynebacterium diphtheriae (J. M. Boyd, M. Oza, and J. R. Murphy, Proc. Natl. Acad. Sci. USA 87:5972, 1990). We report here the molecular cloning, DNA sequence analysis, and characterization of DtxR from the PW8(-), 1030(-), and C7hm723 strains of C. diphtheriae. While the sequence of dtxR from PW8(-) is identical to that of the C7(-) allele, the sequence of dtxR from the 1030(-) strain is only 91.4% identical; however, the deduced amino acid sequence of DtxR from 1030(-) differs by only 6 of 678 amino acids. Moreover, DtxR from all three strains is shown to regulate expression of beta-galactosidase from a tox promoter-operator (toxPO)-lacZ transcriptional fusion. In contrast, the dtxR allele from the iron-insensitive tox constitutive mutant C7hm723 was found to have a single G----A transition, resulting in a substitution of Arg-47 to His and the loss of tox regulatory activity in recombinant Escherichia coli.
authors.affiliation: Evans Department of Clinical Research, University Hospital, Boston University Medical Center, Massachusetts 02118.
authors.forename: J M
authors.initials: JM
authors.lastname: Boyd
authors.forename: K C
authors.initials: KC
authors.lastname: Hall
authors.forename: J R
authors.initials: JR
authors.lastname: Murphy
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D003353:Corynebacterium diphtheriae / Q000235:genetics*; D004167:Diphtheria Toxin / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D007501:Iron / Q000494:pharmacology; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D004167:Diphtheria Toxin; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D007501:Iron; D001616:beta-Galactosidase