Publication: The metamorphic transformation of a water-soluble monomeric
protein into an oligomeric transmembrane pore
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Publication Date
2017
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Eslsevier
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Abstract
Sea anemones produce venoms containing different toxic molecules. Among them, actinoporins are some of the best characterized ones. They constitute a family of toxic polypeptides that belong to the much larger group of pore-forming toxins. Actinoporins remain mostly monomeric and stably folded in aqueous solution but, upon interaction with lipid membranes of specific composition, they become oligomeric integral membrane structures to build a pore. They insert an α-helix stretch within biological membranes, forming cation-selective pores with a diameter of 1–2 nm, which result in a colloid osmotic shock that leads to cell death. They are believed to participate in functions like predation, defense, and digestion and have been shown to be lethal for small crustaceans, mollusks, and fish. The best-known actinoporins are equinatoxin II (from Actinia equina), fragaceatoxin C (from Actinia fragacea), and sticholysins I and II (from Stichodactyla helianthus). In order to fully understand the pore formation mechanism of these proteins, several approaches have been used: (i) characterization of natural and artificial variants of actinoporins to determine the role of specific residues, (ii) study of their water-soluble and transmembrane structures, and (iii) employment of different lipids to evaluate the influence of membrane properties and composition. Further research is still needed, however, in order to fully understand the complex mechanism underlying actinoporins’ functionality.