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  • Title: Kinetics of streptolysin O self-assembly.
    Author: Palmer M, Valeva A, Kehoe M, Bhakdi S.
    Journal: Eur J Biochem; 1995 Jul 15; 231(2):388-95. PubMed ID: 7635150.
    Abstract:
    Streptolysin O is a member of a family of membrane-damaging toxins that bind to cell membranes containing cholesterol and then polymerize to form large pores. We have examined the kinetics of toxin action using 125I-labelled streptolysin O. Binding of toxin monomers to membranes displays first-order kinetics and is reversible; the rate of desorption from red cells shows a marked dependence on temperature. To study oligomerization, toxin was bound to erythrocytes at 0 degrees C. Oligomer formation was then triggered by a sudden temperature shift and stopped by solubilization of membranes with deoxycholate. While at moderately high streptolysin O concentrations oligomerization behaves as a reaction of second order, the kinetic pattern changes with increasing toxin concentration. We show that this can be accounted for by the assumption of a two-step reaction mechanism: two membrane-bound monomers first associate into a start complex, which then is rapidly extended by the sequential addition of further monomers up to the final oligomer size.
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