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Infect. Immun., Apr 1995, 1188-1194, Vol 63, No. 4
I Walev, M Palmer, A Valeva, U Weller and S Bhakdi
Streptolysin O (SLO) is a representative of the family of cholesterol-
binding cytolysins that form large pores in target cell membranes.
Aggregation of the toxin to polymeric structures is required for pore
formation. However, it is not known whether, vice versa, polymers may under
certain circumstances remain nonfunctional, and whether this might be the
cause underlying the relative resistance of certain cells towards toxin
action. In the present study, we applied radioiodinated, functionally
active SLO to human, rabbit, and mouse erythrocytes and to human
fibroblasts and keratinocytes. Binding and polymerization were quantified
and correlated with membrane damage. At low toxin concentrations, human and
rabbit but not mouse erythrocytes were lysed, but binding and
polymerization of SLO were essentially identical in all cases. Nonlytic
polymers were also detected on human fibroblasts and keratinocytes treated
with subcytotoxic concentrations of SLO, and quantitative estimates
indicated that nonpermeabilized cells could carry hundreds of polymers on
their surface. When applied at low concentrations to fibroblasts, much of
the toxin remained in monomer form and was subsequently shed from the
cells. This was shown by monitoring the fate of radioiodinated toxin and
also by using a sensitive cell enzyme-linked immunosorbent assay that
permitted immunological detection of surface-exposed SLO. Thus, relative
resistance of cells towards the permeabilizing action of SLO may be due to
their ability to tolerate formation of a limited number of SLO polymers and
to shedding of nonoligomerized toxin from their surface.
Copyright © 1995, American Society for Microbiology
Binding, oligomerization, and pore formation by streptolysin O in erythrocytes and fibroblast membranes: detection of nonlytic polymers
Institute of Medical Microbiology and Hygiene, Mainz, Germany.
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