Diphtheria toxin 5505849 226066143 2008-07-16T17:57:51Z 79.6.9.197 '''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]] [[de:Diphtherietoxin]] [[pl:Toksyna błonicza]] [[ro:Toxina difterică]] [[it:Tossina difterica]]