Assembly of Staphylococcus aureus gamma-hemolysin into a pore-forming ring-shaped complex on the surface of human erythrocytes.

Staphylococcal gamma-hemolysin consists of Hlg1 (or Luk F) of 34 kDa and Hlg2 of 32 kDa, which cooperatively lyse human erythrocytes. Since gamma-hemolysin caused swelling of human erythrocytes prior to lysis, we studied pore-forming nature of the toxin by use of polyethylene glycols as osmotic protectants and determined the functional diameter of the pore. To elucidate the molecular architecture of the membrane pore formed by gamma-hemolysin, we solubilized the pore complex with 2% sodium dodecyl sulfate, separated it from erythrocyte membrane proteins by sucrose gradient ultracentrifugation, and observed the isolated complex under an electron microscope. Our data showed that Hlg1 and Hlg2 of gamma-hemolysin assemble into a ring-shaped 195 kDa complex in a molar ratio of 1 : 1, which may form a membrane pore with a functional diameter of 2.1-2.4 nm.