Alpha-toxin, also known as alpha-hemolysin (Hla), is the major cytotoxic agent released by bacterium Staphylococcus aureus and the first identified member of the pore forming beta-barrel toxin family. This toxin consists mostly of beta sheets (68%) with only about 10% alpha helices. The hly gene on the S. aureus chromosome encodes the 293 residue protein monomer, which forms heptameric units on the cellular membrane to form a complete beta barrel pore. This structure allows the toxin to perform its major function, development of pores in the cellular membrane, eventually causing cell death.