Structure
The structure of several hemolysins has been solved by X-ray crystallography in the soluble and pore-forming conformations. For example, α-hemolysin of Staphylococcus aureus forms a homo-heptameric β-barrel in biological membranes. The Vibrio cholerae cytolysin also forms a heptameric pore, however Staphylococcus aureus γ-hemolysin forms a pore which is octomeric.
Thanks to latest research on the field of hemolysin's structure, we do know that the structure of the Staphylococcus aureus α-hemolysin pore has been determined to 1.9 Å resolution. Contained within the mushroom-shaped homo-oligomeric heptamer is a solvent-filled channel, 100 Å in length, that runs along the sevenfold axis and ranges from 14 Å to 46 Å in diameter. Furthermore, the structure proves the heptameric subunit stoichiometry of the α-hemolysin oligomer, shows that a glycine-rich and solvent-exposed region of a water-soluble protein can self-assemble to form a transmembrane pore of defined structure, and provides insight into the principles of membrane interaction and transport activity of β barrel pore-forming toxins.
The structure of the detergent-solubilized heptamer has been determined by X-ray crystallography to 1.9 Å resolution. The heptamer has a mushroom-like shape and measures up to 100 Å in diameter and 100 Å in height. Spanning the length of the molecule and coincident with the molecular sevenfold axis is a water-filled channel that ranges in diameter from 16 to 46 Å. A 14 strand antiparallel β barrel. On the exterior of the β barrel there is a hydrophobic belt approximately 30 Å in width that provides a surface complementary to the nonpolar portion of the lipid bilayer. The interfaces are composed of both salt-links and hydrogen bonds, as well as hydrophobic interactions, and these contacts provide a molecular stability for the heptamer in SDS solutions even up to 65°C.
Read more about this topic: Hemolysin
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