ALPHA-HEMOLYSIN, GAMMA-HEMOLYSIN, AND LEUKOCIDIN FROM STAPHYLOCOCCUS-AUREUS - DISTANT IN SEQUENCE BUT SIMILAR IN STRUCTURE

alpha-Hemolysin from Staphylococcus aureus assembles from a water-solu ble, monomeric species to a membrane-bound heptamer on the surface of target cells, creating water-filled channels that lead to cell death a nd lysis. Staphylococcus aureus also produces the gamma-hemolysin and leukocidin toxins, which function as two component toxins in the disru ption and lysis of erythrocytes and leukocytes. Analysis of the aligne d sequences of alpha-hemolysin, gamma-hemolysin, and leukocidin in the context of the alpha-hemolysin heptamer structure supports the conclu sion that even though the level of sequence identity between cu-hemoly sin and the gamma-hemolysin and leukocidin toxins is in the so-called twilight zone, the three-dimensional structures of the protomers are p robably conserved. By analogy with alpha-hemolysin, gamma-hemolysin an d leukocidin may also form oligomeric, transmembrane channels in which an antiparallel beta-barrel constitutes the primary membrane-embedded domain.