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Nature. 2004 May 27;429(6990):429-33.

Assembly and function of a bacterial genotoxin.

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Laboratory of Structural Microbiology, The Rockefeller University, New York 10021, USA.


The tripartite cytolethal distending toxin (CDT) induces cell cycle arrest and apoptosis in eukaryotic cells. The subunits CdtA and CdtC associate with the nuclease CdtB to form a holotoxin that translocates CdtB into the host cell, where it acts as a genotoxin by creating DNA lesions. Here we show that the crystal structure of the holotoxin from Haemophilus ducreyi reveals that CDT consists of an enzyme of the DNase-I family, bound to two ricin-like lectin domains. CdtA, CdtB and CdtC form a ternary complex with three interdependent molecular interfaces, characterized by globular, as well as extensive non-globular, interactions. The lectin subunits form a deeply grooved, highly aromatic surface that we show to be critical for toxicity. The holotoxin possesses a steric block of the CdtB active site by means of a non-globular extension of the CdtC subunit, and we identify putative DNA binding residues in CdtB that are essential for toxin activity.

[Indexed for MEDLINE]

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