Properties of a hemolysin produced by group B streptococci

Abstract

The hemolysin produced by group B streptococci (GBH) has an isoelectric point (pI) of 5.8 and it shows a hemolytic activity in the absence of 2-mercaptoethanol (2-ME). The hemolytic activities of GBH were compared to that of streptolysin O (SLO) and streptolysin S (SLS). These hemolysins differed with respect to the binding and release of hemoglobin (Hb). GBH was bound to phospholipids on the membranes of target erythrocytes, followed by the gentle release of K+ and slow Hb release without lag time. Incontrast SLO released Hb as rapidly as K+. GBH induced hemolysis was inhibited by the addition of 30 mM raffinose. These results indicate that the effective diameter of the pores formed by GBH was about 1.1 nm. GBH showed a lower hemolytic efficiency than SLO, reflecting the fact that these hemolysins destroy erythrocytes by a different mechanism. Intracellular K+ and Hb were released at a different rate in GBH treated cells, indicating that a colloid-osmotic process is involved in the lytic mechanism.