MOLECULAR-BIOLOGY OF THE PORE-FORMING CYTOLYSINS FROM STAPHYLOCOCCUS-AUREUS, ALPHA-HEMOLYSINS AND GAMMA-HEMOLYSINS AND LEUKOCIDIN

Staphylococcus aureus is an important opportunistic pathogen. It produ ces a variety of extracellular proteins, which may play important role s in infections by this bacterium. Staphyloccal alpha-toxin is a pore- forming 33-kDa polypeptide. In the first part of this article, we will refer to the roles of cell membranes in the pore formation by alpha-t oxin as well as the molecular dissection of alpha-toxin for understand ing its pore-forming nature, Staphylococcal gamma-hemolysin and leukoc idin are bi-component cytolysins, which have different cell specificit ies towards erythrocytes and leukocytes, respectively, We have found t hat these bi-component cytolysins share a common component, In the sec ond part of this article, we will refer to the current status of knowl edge of molecular cloning of the genes coding for gamma-hemolysin and leukocidin, molecular domains of the toxins which decide the cell spec ificities, and mode of action of these bi-component toxins.