Pore Streptolysin

When alamethicin is added to a ternary vesicle system comprising PDA, phospholipid, and lipopolysaccharide (LPS), the addition of polymyxin, an LPS-binding antibiotic, sensitizes the vesicles to alamethicin (Katz et al. 2003). Cholesterol-containing PDA liposomes have been used to colorimetrically detect streptolysin O, a cholesterol-dependent pore-forming toxin (Ma and Cheng 2005). 

Certain cellular processes are specifically influenced by gradients of monovalent ions across the plasma membrane. It appears that stimulation of some such processes are actually counteracted by concomitant flux. Ca -dependent processes in turn may be abrogated when pores are large enough to permit rapid egress of cytoplasmic proteins. Therefore, it is useful to differentiate between three types of pores (a) those that are selectively permissive for monovalent ions (e.g. staphylococcal alpha-toxin) (b) those that are permissive for Ca and small molecules, but not for proteins (e.g. E. coli hemolysin) and (c) large pores that allow passage of macromolecules (e.g. streptolysin O). 

When very large pores are needed, streptolysin O is presently the most convenient toxin to apply. Streptolysin O pores are so large that cytoplasmic proteins rapidly egress from the cells however, intracellular organelles and the cytoskeleton remain, so that key cellular processes such as vesicle trafficking and movement of peptides amongst cellular compartments can be analyzed, e.g. with the use of antibodies. 

Bhakdi S, Bayley H, Valeva A etal. (1996) Staphylococcal alpha-toxin, streptolysin O, and Escherichia coli hemolysin prototypes of pore forming bacterial cytoly-sins. In Arch Microbiol 165 73-79. 

Permeabilized cells allow the study of intracellular processes in situ under conditions which are believed to be close to the physiological situation in intact cells. Permeabilization by bacterial pore-forming toxins, alpha-toxin and streptolysin O (SLO) is now a widely accepted approach in the functional analysis of intracellular organelles. 

Walev I, Hombach M, Bobkiewicz W, Fenske D, Bhakdi S, Husmann M (2002) Resealing of large transmembrane pores produced by streptolysin O in nucleated cells is accompanied by NF-kappa B activation and downstream events. FASEB J 16(2) 237-239... 

Toxins that act directly on cell membranes, called cytolytic toxins, disturb and ultimately kill the target cells. Produced by many organisms (e.g., bacteria, fungi, plants, fish, and snakes), cytolytic toxins may cause damage in several ways. For example, streptolysin O (67,000 D), produced by the bacterium Streptococcus pyogenes, causes pores to form in the target cell membranes. Affected cells are rapidly lysed because the cell membrane is much more permeable to ions such as Na+. Streptolysin O is believed to cause some of the damage in rheumatic fever. 

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