20.500.12556/RUL-152844 Bacillus thuringiensis toxin Cyt2Aa forms filamentous oligomers when exposed to lipid membranes or detergents The bacterium Bacillus thuringiensis (Bt) produces insecticidal proteins during the sporulation phase. These proteins are located in parasporal crystals consisting of two delta-endotoxin classes, crystal (Cry) and cytolytic (Cyt) toxins. In vitro, Cyt toxins show cytolytic activity against bacterial and a variety of insect and mammalian cells. They bind to cell membranes with unsaturated phospholipids and sphingomyelin. Although Bt and its parasporal crystals containing both Cry and Cyt toxins have been successfully used as bioinsecticides, the molecular mechanism of action of Cyt toxins is not yet fully understood. To address this, we exposed Cyt2Aa to lipid membranes and visualized membrane disruption process using cryo-electron microscopy. We observed two types of Cyt2Aa oligomers. First, Cyt2Aa forms smaller curved oligomers on the membrane surface that become linear over time, and detach when the membrane ruptures. Similar linear filamentous oligomers were also formed by Cyt2Aa in the presence of detergents without prior exposure to lipid membranes, which exhibited attenuated cytolytic activity. Furthermore, our data suggest that Cyt2Aa adopts different conformations between its monomeric and oligomeric forms. Overall, our results provide new evidence for a detergent-like mechanism of action of Cyt2Aa rather than the pore-forming model of target membrane disruption of this important class of insecticidal proteins. Bacillus thuringiensis parasporal crystal delta-endotoxins Cyt toxin Cyt2Aa oligomers detergent-like mechanism of action biokemija bakterije bacili toksini lipidne membrane oligomeri true false true Angleški jezik Slovenski jezik Članek v reviji 2023-12-08 15:22:41 2023-12-08 15:22:41 2023-12-11 09:51:01 0000-00-00 00:00:00 2023 0 0 Str. 44-52 Vol. 674 24 Sep. 2023 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 577 1090-2104 10.1016/j.bbrc.2023.06.078 158413827 1-s2.0-S0006291X23008331-main.pdf 1-s2.0-S0006291X23008331-main.pdf 1 BE06B8B28D909232FFD4F42419FEEA06 01950b9b788bbd5246e2f76ded230d0f5292a0b490868646a3deff2b1a355b6d 8f9d6f08-95d5-11ee-9c20-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=178535 https://www.sciencedirect.com/science/article/pii/S0006291X23008331 1 3fdcddbb-95d5-11ee-9c20-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=178534 Biotehniška fakulteta 0 0 0