Aerolysin
In molecular biology, aerolysin is a cytolytic pore-forming toxin exported by Aeromonas hydrophila, a Gram-negative bacterium associated with diarrhoeal diseases and deep wound infections. It is also produced by the caterpillar of the moth Megalopyge opercularis, sometimes called the Tree Asp. The mature toxin binds to eukaryotic cells and aggregates to form holes (approximately 3 nm in diameter) leading to the destruction of the membrane permeability barrier and osmotic lysis. The structure of proaerolysin has been determined to 2.8A resolution and shows the protoxin to adopt a novel fold. Images of an aerolysin oligomer derived from electron microscopy have helped to construct a model of the protein in its  heptameric conformation, and to outline a mechanism by which this assembly might insert into lipid bilayers to form ion channels. References

Protein domains