Diphtheria toxin
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'''Diphtheria toxin''' is an [[exotoxin]] secreted by ''[[Corynebacterium diphtheriae]]'', the [[pathogen]] [[bacteria|bacterium]] that causes [[diphtheria]].
==Structure==
Diphtheria toxin is a single [[polypeptide]] chain of 535 amino acids consisting of two [[subunits]] linked by [[disulfide bridge]]s. Binding to the cell surface of the less stable of these two subunits allows the more stable part of the protein to penetrate the [[Host (biology)|host cell]].<ref name=Baron>{{cite book | author = Murphy JR | title = ''Corynebacterium Diphtheriae'': Diphtheria Toxin Production ''In:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | id = [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1752 (via NCBI Bookshelf)] ISBN 0-9631172-1-1 }}</ref>
==Mechanism==
It catalyzes the [[ADP ribosylation factor|ADP-ribosylation]] eukaryotic [[elongation factor]]-2 (eEF2), inactivating this protein. It does so by ADP-ribosylating the unusual [[aminoacid]] [[diphthamide]]. In this way, it acts as a [[Translation_%28genetics%29|RNA translational]] inhibitor. The [[exotoxin A]] of [[Pseudomonas aeruginosa]] uses a similar mechanism of action.
==Lethal dose==
Diphtheria toxin is extraordinarily potent.<ref name=Baron /> The [[Lethal_dose|lethal dose]] for humans is about 0.1 μg of toxin per kg of bodyweight. A massive release of toxin into the body will likely cause lethal [[necrosis]] of the [[heart]] and [[liver]].<ref name=Pappenheimer_1977>{{cite journal | author = Pappenheimer A | title = Diphtheria toxin. | journal = Annu Rev Biochem | volume = 46 | issue = | pages = 69–94 | year = 1977 | pmid = 20040 | doi = 10.1146/annurev.bi.46.070177.000441}}</ref>
==History==
Diphtheria toxin was discovered in 1890 by [[Von_Behring|Emil Adolf von Bering]].
==Clinical use==
The drug [[denileukin diftitox]] uses diphtheria toxin as an antineoplastic agent.
==References==
<references />
==External links==
* {{MeshName|Diphtheria+Toxin}}
{{Glycosyltransferases}}
[[Category:Peripheral membrane proteins]]
[[Category:Toxins]]
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