group of haemolytic exotoxins released by streptococci. _ haemolysin: 26-39 kd (four types), forms ring like structures in membranes (see streptolysin O). Lipid target unclear. _ haemolysin: a hot cold haemolysin with sphingomyelinase C activity. _ haemolysin: complex of two proteins (29 and 26 kD) that act synergistically, rabbit erythrocytes particularly sensitive. _ toxin: heat stable peptide (5 kD) with high proportion of hydrophobic amino acids. Seems to act in a detergent like manner (c.f. Subtilysin), but may form hydrophilic transmembrane pores by cooperative interaction with other _ toxin molecules. Leucocidin (panton valentine leucocidin): two components f (fast migration on CM cellulose column: 32 kD) and s (slow: 38 kD). Mode of action contentious.