Pore-forming toxins
| Leukocidin | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Leukocidin | ||||||||
| Pfam | PF07968 | ||||||||
| InterPro | IPR001340 | ||||||||
| TCDB | 1.C.3 | ||||||||
| OPM superfamily | 35 | ||||||||
| OPM protein | 7ahl | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
Pore-forming proteins (Also known as Pore-forming toxins) are protein exotoxins, usually 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.
PFTs can be divided into the following subcategories:
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:
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.
β-PFTs are dimorphic proteins that exist as soluble monomers and then assemble to form multimeric assemblies that constitute the pore. Figure 1 shows the pore-form of α-Hemolysin, the first crystal structure of a β-PFT in its pore-form. 7 α-Hemolysin monomers come together to create the mushroom-shaped pore. The 'cap' of the mushroom sits on the surface of the cell, and the 'stalk' of the mushroom penetrates the cell membrane, rendering it permeable (see later). The 'stalk' is composed of a 14-strand β-barrel, with two strands donated from each monomer.
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