Fig. 1.

Schematic representation of the alternative pore forming mechanisms for α− and β−PFTs. (a) Most α−PFTs bind to specific receptors and once a critical concentration is reached PFT subunits insert concomitantly into the membrane and oligomerise to form the final pore. This mechanism of pore formation can sometimes result in formation of an incomplete pore that, none-the-less, retains function. (b) Protomers of most β−PFTs instead, following their concentration at the membrane interface, accumulate into a structure known as the pre-pore. Once oligomerisation is complete, the pre-pore subunits undergo massive conformational change to concertedly insert into the membrane.