Interaction of streptolysin O from Streptococcus pyogenes and theta-toxin from Clostridium perfringens with human fibroblasts

Abstract

The membrane-damaging properties on human diploid embryonic lung fibroblasts of streptolysin O (from S. pyogenes) and .theta.-toxin (from C. perfringens) were compared. The results are consistent with the suggested mechanism for hemolysis by streptolysin O involving 1 fixation site and 1 lytic site of this cytolysin. The membrane-damaging activity of the 2 toxins differed with respect to relative cytolytic activity on human diploid lung fibroblasts compared with that on sheep erythrocytes, binding to the fibroblast membrane, activity at 0.degree. C, membrane repair after more than 30 min and effect on influx of amino acids. The mechanism of membrane damage caused by .theta.-toxin differs from that of streptolysin O, since the former toxin was active at 0.degree. C and did not bind to the cytoplasmic membrane. These results question the current concept that all thiol-activated, cholesterol-inactivated bacterial toxins are similar both structurally and functionally.