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Deng, K, Latimer, JL, Lewis, DA and Hansen, EJ (2001) Investigation of the interaction among the components of the cytolethal distending toxin of Haemophilus ducreyi. Biochem. Biophys. Res. Commun. 285:609-15


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.


PubMed Online version:10.1006/bbrc.2001.5223


Bacterial Toxins/chemistry; Bacterial Toxins/genetics; Bacterial Toxins/metabolism; Biological Assay; Blotting, Western; Chromatography, Affinity; Electrophoresis, Polyacrylamide Gel; Escherichia coli/genetics; Haemophilus ducreyi; HeLa Cells; Humans; Immunosorbent Techniques; Macromolecular Substances; Protein Binding; Protein Subunits; Recombinant Proteins/chemistry; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Structure-Activity Relationship



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0001907: killing by symbiont of host cells



Figure 2D shows that the eluate of a cdtA mutant strain is not detectably cytotoxic. Cytotoxicity can be restored by mixture of CdtB and CdtC with the sonicated cell lysate of E. coli expressing cdtA. This recovery was not seen upon combination of CdtB and CdtC alone or with the sonicated cell lysate of E.coli carrying a control plasmid (Figure 4, especially 4G vs 4FH).

CACAO 5295

See also


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