The fruiting bodies of fungi are known sources of pore forming proteins (PFPs). These PFP become active upon ingestion by unsuspecting insects or nematode species, where it is hypothesised that oligomerisation of the pore forming protein occurs in the mid-gut tissues. This activation is postulated to lead to wide-spread tissue damage and ultimately killing of the insect or worm. One putative PFP that has recently been discovered from the mushroom Coprinopsis cinerea, is referred to here as coprinolysin (CC1G_11805). Coprinolysin is predicted to belong to the aerolysin/ETX-like PFP which are characterised by formation of 2 - 3 nm sized ß-barrel pores in the respective target cells. All family members generally contain a common domain responsible for oligomerisation and pore formation. They also contain one or more domains responsible for the recognition of receptors or membranes and can be used to define sub-families.
Here, we determined the structure of a putative packaging assembly of coprinolysin which we postulate resembles the higher order state from the mushroom fruiting body. The assembly, arranged in this way, may ensure the delivery of high-concentrations of coprinolysin to the target tissue. While the mechanism of coprinolysin function remains elusive to date, we identified an aerolysin-like pre-pore assembly in two-subunits within the crystal structure which may suggest a mode of oligomerisation through the pore forming domain. Taken together, these results suggest coprinolysin is an insect-targeting pore forming protein from the aerolysin/ETX-family. This may represent a novel insecticidal agent for future development.