Cytolethal distending toxin
| Cytolethal distending toxin | |||||||||
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Crystal structure of the fully assembled Haemophilus ducreyi cytolethal distending toxin
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| Identifiers | |||||||||
| Symbol | CDT | ||||||||
| Pfam | PF03498 | ||||||||
| Pfam clan | CL0066 | ||||||||
| InterPro | IPR003558 | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
Cytolethal distending toxins (abbreviated CDTs) are a class of heterotrimeric toxins produced by certain gram-negative bacteria that display DNase activity. These toxins trigger G2/M cell cycle arrest in specific mammalian cell lines, leading to the enlarged or distended cells for which these toxins are named. Affected cells die by apoptosis.
Each toxin consists of three distinct subunits named alphabetically in the order that their coding genes appear in the cdt operon. Cytolethal distending toxins are classified as AB toxins, with an active ("A") subunit that directly damages DNA and a binding ("B") subunit that helps the toxin attach to the target cells. CdtB is the active subunit and a homolog to mammalian DNase I, whereas CdtA and CdtC make up the binding subunit.
Cytolethal distending toxins are produced by gram-negative pathogenic bacteria from the phylum Proteobacteria. Many of these bacteria, including Shigella dysenteriae, Haemophilus ducreyi, and Escherichia coli, infect humans. Bacteria that produce CDTs often persistently colonize their host.
The first recorded observation of a cytolethal-distending toxin was in 1987 in a pathogenic strain in E. coli isolated from a young patient. Later that year, scientists W.M. Johnson and H. Lior published the journal article “Production of Shiga toxin and a cytolethal distending toxin (CLDT) by serogroups of Shigella spp.” In Microbiology Letters. The discovery of other bacteria producing CDT toxins continues to this day.
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