In molecular biology, the sea anemone cytotoxic proteins are lethal pore-forming proteins, known collectively as actinoporins, a sub-class of cytolysins. There are several different groups of cytolysins based on their structure and function. This entry represents the most numerous group, the 20kDa highly basic peptides. These cytolysins form cation-selective pores in sphingomyelin-containing membranes. Examples include equinatoxins, sticholysins, magnificalysins, and tenebrosins, which exhibit pore-forming, haemolytic, cytotoxic, and heart stimulatory activities.
Structure
Actinoporins are small (~20 kDa) pore-forming proteins produced by sea anemones. Their structure consists of a β-sandwich core flanked by two α-helices. One of these α-helices, located at the N-terminus, is flexible in solution and plays a critical role in membrane insertion during pore formation. The overall fold is highly conserved among actinoporins and is critical for their ability to interact with lipid membranes. == Pore formation mechanism ==
Pore formation mechanism
Actinoporins exert their cytolytic activity by recognizing sphingomyelin-rich membranes. Upon binding, the flexible N-terminal α-helix inserts into the membrane lipid bilayer. == Isoforms and genetic diversity ==
Isoforms and genetic diversity
Many sea anemone species produce multiple actinoporin isoforms through gene duplication and diversification. These isoforms often vary slightly in their amino acid sequences, which can alter their pore-forming efficiency and cytolytic activity. For example, species like Actinia equina, Heteractis crispa, and Stichodactyla helianthus produce multiple distinct actinoporins with different biochemical properties. == References ==