pore-forming module of Thalassophryne nattereri fish venom natterins 1-4, and similar aerolysin-type beta-barrel pore-forming proteins
This group includes 4 of the 5 Thalassophryne nattereri fish venom natterins: natterin-1, -2, -3, and 4. Natterins have kininogenase activity, kallikrein activity, and are allodynic and edema inducing. They also cleave type I and type IV collagen, resulting in necrosis of the affected cells. Contradictory to their edematic activity, Natterins also have anti-inflammatory effects through inhibition of interactions between leukocytes and the endothelium, and reduction in neutrophil accumulation. Many proteins belonging to this group have an N-terminal DUF3421 domain. 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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