title: Molecular cloning and DNA sequence analysis of a diphtheria tox iron-dependent regulatory element (dtxR) from Corynebacterium diphtheriae.
abstract: Although the structural gene for diphtheria toxin, tox, is carried by a family of closely related corynebacteriophages, the regulation of tox expression is controlled, to a large extent, by its bacterial host Corynebacterium diphtheriae. Optimal yields of tox gene products are obtained only when iron becomes the growth-rate-limiting substrate. Previous studies suggest that regulation of tox expression is mediated through an iron-binding aporepressor. To facilitate molecular cloning of the tox regulatory element from genomic libraries of C. diphtheriae, we constructed a tox promoter/operator (toxPO)-lacZ transcriptional fusion in Escherichia coli strain DH5 alpha. We report the molecular cloning and nucleic acid sequence of a diphtheria tox iron-dependent regulatory element, dtxR, and demonstrate that expression of beta-galactosidase from the toxPO-lacZ fusion is regulated by dtxR-encoded protein in an iron-sensitive manner. In addition, we show that expression of the toxPO-lacZ fusion is not affected by the E. coli iron-regulatory protein Fur and that the dtxR protein does not inhibit expression of fur-regulated outer-membrane proteins.
authors.affiliation: Evans Department of Clinical Research, Boston University Medical Center, MA 02118.
authors.forename: J
authors.initials: J
authors.lastname: Boyd
authors.forename: M N
authors.initials: MN
authors.lastname: Oza
authors.forename: J R
authors.initials: JR
authors.lastname: Murphy
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003353:Corynebacterium diphtheriae / Q000187:drug effects / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D004167:Diphtheria Toxin / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005838:Genotype; D007501:Iron / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D015183:Restriction Mapping
chemical_list: D004269:DNA, Bacterial; D004167:Diphtheria Toxin; D007501:Iron