Pore-forming toxin
Pore-forming toxins (PFTs) are protein exotoxins, typically (but not exclusively) produced by bacteria, such as C.septicum and S.aureus. They are frequently cytotoxic (i.e., they kill cells), as they create unregulated pores in the membrane of targeted cells.
Types of PFTs
PFTs can be divided into the following subcategories:
- e.g., Cytolysin A of E. coli.
- e.g., α-hemolysin (Fig 1), PVL- Panton-Valentine leukocidin.
Above are the two main distinctions of PFTs. They differ in the suspected mode of membrane integration, either by alpha-helical or beta-sheet elements.
Other Categories:
- e.g., Anthrax toxin
- e.g., Pneumolysin
- e.g., Gramicidin A
Beta-pore-forming toxins
β-PFTs are so-named because of their structural characteristics: they are composed mostly of β-strand-based domains. Whilst they frequently have divergent sequences, many are classified by Pfam as Leukocidins. X-ray crystallographic structures have revealed some commonalities: α-hemolysin and Panton-Valentine leukocidin S are structurally related, as are aerolysin and Clostridial Epsilon-toxin.
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