Pore-forming toxin that contributes to the virulence of P.entomophila against Drosophila, playing an important role in host intestinal damage and lethality. Displays cytolytic and hemolytic activity. Pro-Monalysin forms a stable donut-like 18-mer complex composed of two disk-shaped nonamers held together by N-terminal swapping of the pro-peptides (PubMed:25847242). After proteolytic cleavage, the inactive 18-mer complex probably dissociates into two disk-shaped active nonamers in which the transmembrane segments are unmasked and ready to engage the conformational change leading to the pore formation into the target membrane (PubMed:25847242). Multimerizes into circular-like structures and barrel-like aggregates (PubMed:21980286). Is regulated by both the GacS/GacA two-component system and the Pvf regulator, two signaling systems that control P.entomophila pathogenicity. Monalysin structure belongs to the Aerolysin-like PFTs fold family but is devoid of obvious receptor-binding domain. Requires N-terminal cleavage to become fully active. The metalloprotease AprA can induce the rapid cleavage of pro-Monalysin into its active form. Can also be processed by trypsin. Reduced cell death is observed upon infection with a mutant deficient in Monalysin production. This mutant is affected in its abilities to induce cell damage in the Drosophila gut. It induces lower level of stress and repair pathway activity than wild-type.