AB toxin

• DT-like toxins: all toxins of these class are ADP-ribosyltransferases, which means they damage the cell by attaching an ADP-ribose moiety onto important target components: in this case eEF2.{{cite journal |last1=Simon |first1=NC |last2=Aktories |first2=K |last3=Barbieri |first3=JT |title=Novel bacterial ADP-ribosylating toxins: structure and function. |journal=Nature Reviews. Microbiology |date=September 2014 |volume=12 |issue=9 |pages=599–611 |doi=10.1038/nrmicro3310 |pmid=25023120|pmc=5846498 }}
• The Diphtheria toxin (DT) is an AB toxin. It inhibits protein synthesis in the host cell through ADP-ribosylation of the eukaryotic elongation factor 2 (eEF2), which is an essential component for protein synthesis. It is slightly unusual in that it combines the A and B parts in the same protein chain: the pre-toxin is cleaved into two parts, then the two parts are joined by a disulfide bond.
• The exotoxin A of Pseudomonas aeruginosa is another example of an AB toxin that targets the eEF2. The "A" part is structurally similar to the DT "A" part; the "B" part is located to the N-terminal direction to the "A" part, unlike DT. The bioinformatically-identified "Cholix" toxin from V. cholerae is similar.
• AB7 toxins: all toxins of this class share a related heptameric "B" subunit, but differ in the function of their "A" part.
• C2-like toxins: the "A" parts are G-actin ADP-ribosyltransferases, which carry out a modification that prevents actin from polymerizing. Members include C. botulinum{{cite journal | vauthors = Fujii N, Kubota T, Shirakawa S, Kimura K, Ohishi I, Moriishi K, Isogai E, Isogai H | title = Characterization of component-I gene of botulinum C2 toxin and PCR detection of its gene in clostridial species | journal = Biochem. Biophys. Res. Commun. | volume = 220 | issue = 2 | pages = 353–9 |date=March 1996 | pmid = 8645309 | doi = 10.1006/bbrc.1996.0409 }} C. perfringens iota toxin and Clostridioides difficile ADP-ribosyltransferase.{{cite journal | vauthors = Stubbs S, Rupnik M, Gibert M, Brazier J, Duerden B, Popoff M | title = Production of actin-specific ADP-ribosyltransferase (binary toxin) by strains of Clostridium difficile | journal = FEMS Microbiol. Lett. | volume = 186 | issue = 2 | pages = 307–12 |date=May 2000 | pmid = 10802189 | doi = 10.1111/j.1574-6968.2000.tb09122.x| doi-access = free }}
• Anthrax toxins: The protective antigen (PA) is the "B" component shared by the two "A" toxins in B. anthracis: the edema factor (EF) and the lethal factor (LF).{{cite journal | vauthors = Pezard C, Berche P, Mock M | title = Contribution of individual toxin components to virulence of Bacillus anthracis | journal = Infect. Immun. | volume = 59 | issue = 10 | pages = 3472–7 |date=October 1991 | pmid = 1910002 | pmc = 258908 | doi = 10.1128/IAI.59.10.3472-3477.1991}}{{cite journal | vauthors = Welkos SL, Lowe JR, Eden-McCutchan F, Vodkin M, Leppla SH, Schmidt JJ | title = Sequence and analysis of the DNA encoding protective antigen of Bacillus anthracis | journal = Gene | volume = 69 | issue = 2 | pages = 287–300 |date=September 1988 | pmid = 3148491 | doi =10.1016/0378-1119(88)90439-8 | url = http://www.dtic.mil/get-tr-doc/pdf?AD=ADA204674| archive-url = https://web.archive.org/web/20170923033835/http://www.dtic.mil/get-tr-doc/pdf?AD=ADA204674| url-status = dead| archive-date = September 23, 2017| url-access = subscription }} LF is a Zn metalloprotease that cleaves MAPKK; EF is an adenylate cyclase that targets protein kinases.
• AB5 toxins – all these toxins share a related pentameric "B" subunit, but differ in the function of their "A" part.
• Ricin is expressed a single polypeptide that gets cleaved into two parts, one acting as "A" and the other acting as "B". Abrin is similar.
• Clostridium neurotoxins, i.e. the tetanus toxin and the botulinum toxin, are expressed a single polypeptide that gets cleaved into two parts, one acting as "A" and the other acting as "B".

The two-phase mechanism of action of AB toxins is of particular interest in cancer therapy research. The general idea is to modify the B component of existing toxins to selectively bind to malignant cells. This approach combines results from cancer immunotherapy with the high toxicity of AB toxins, giving raise to a new class of chimeric protein drugs, called immunotoxins.{{cite journal |vauthors=Zahaf N, Schmidt G |date=2017-07-18 |title=Bacterial Toxins for Cancer Therapy |journal=Toxins (Basel) |volume=9 |issue=8 |pages=236 |doi=10.3390/toxins9080236 |pmc=5577570 |pmid=28788054 |doi-access=free }}

• Toxalbumin
• Perivitellin-2

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{{Toxins}}

{{InterPro content|IPR003540}}

{{InterPro content|IPR003896}}

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Category:Bacterial toxins

Category:Protein families