pore-forming module of Bacillus thuringiensis insecticidal Cry51A toxin, Bacillus thuringiensis cytotoxic parasporin-5 and similar aerolysin-type beta-barrel pore-forming proteins
Bacillus thuringiensis parasporin-5 has strong cytocidal activity against several types of cancer cells and may or may not have insecticidal activity. Cry51A toxin is toxic to coleopteran (beetle) larvae. Other members of this family include Bacillus thuringiensis Cry15Aa which is toxic to lepidopteran (butterflies and moth) larvae. They belong to the aerolysin family of beta-pore-forming proteins (beta-PFPs). PFPs are generally secreted as water-soluble monomers, which upon binding to target lipid membranes, oligomerize and form transmembrane pores harmful to cells. Beta-PFPs form pores by transmembrane beta-barrels. Aerolysin-type beta-PFPs are believed to use an amphipathic beta-hairpin to form the beta-barrel, are found in all kingdoms of life and many are bacterial toxins. In addition to having a role in microbial infection, they have potential as biotechnological sensors and delivery systems. They share a similar monomeric architecture, with a variable membrane-binding domain and a structurally conserved pore-forming region. A significant portion of the monomeric subunit structure is re-organized to form the pore. Oligomers formed by members of the aerolysin family include: hepta- (aerolysin), octa- (Dln1), and nonameric oligomers (lysenin and monalysin).
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