Inhibitory effect of C-reactive protein on streptolysin O-mediated hemolytic activity. Comparison of conformational variants

It is shown that C-reactive protein binds to streptolysin O, an exotoxin of hemolytic streptococcus, and neutralizes its hemolytic activity. Incubation of C-reactive protein with the working dose of streptolysin O for 15–20 min at 37°C abolished the hemolysis of subsequently added erythrocytes. The concentration of C-reactive protein that reduced hemolysis by 50% was on average equal to 2.28±0.19 μg/ml. C-reactive protein antihemolytic activity was not affected by blocking of its phosphorylcholine-specific sites with free phosphorylcholine, but decreased as a result of blocking with pneumococcal C-polysaccharide and, particularly, with L-α-phosphatidylcholine. This indicates a hydrophobic nature of C-reactive protein-streptolysin O interaction. C-reactive protein subunits retained antihemolytic activity, while the aggregated C-reactive protein lost part of it. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 5 pp. 506–509, May, 1995 Presented by A. A. Totolyan, Member of the Russian Academy of Medical Sciences