title: Investigation of the interaction among the components of the cytolethal distending toxin of Haemophilus ducreyi.
abstract: The cytolethal distending toxin (CDT) of Haemophilus ducreyi is encoded by the cdtABC genes, but the composition of active CDT is not known. Both immunoaffinity and metal affinity chromatographic methods were used to purify H. ducreyi CDT from recombinant Escherichia coli strains bearing wild-type or mutated H. ducreyi cdtABC genes. Both affinity-purified preparations contained CdtA, CdtB, and CdtC proteins. These purification efforts also revealed that the formation of a noncovalent CdtB-CdtC complex and production of a fully active CDT complex required the presence of a functional CdtA protein. When purified recombinant CdtB and CdtC proteins were mixed, only very slight CDT activity was detected. In contrast, when a bacterial cell extract containing CdtA was mixed with purified preparations of both CdtB and CdtC, full CDT activity was reconstituted in vitro. These results indicate that CdtA is essential for normal H. ducreyi CDT activity and that CdtA likely modifies or alters either CdtB or CdtC or both to form the active CDT complex.
authors.affiliation: Department of Microbiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
authors.forename: K
authors.initials: K
authors.lastname: Deng
authors.forename: J L
authors.initials: JL
authors.lastname: Latimer
authors.forename: D A
authors.initials: DA
authors.lastname: Lewis
authors.forename: E J
authors.initials: EJ
authors.lastname: Hansen
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001681:Biological Assay; D015153:Blotting, Western; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D006191:Haemophilus ducreyi; D006367:HeLa Cells; D006801:Humans; D007163:Immunosorbent Techniques; D046911:Macromolecular Substances; D011485:Protein Binding; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001427:Bacterial Toxins; D046911:Macromolecular Substances; D021122:Protein Subunits; D011994:Recombinant Proteins; C067044:cytolethal distending toxin