Properties of the Gamma Haemolysin of Staphylococcus aureus 'Smith 5R'

Abstract

Purified .gamma. hemolysin of S. aureus was characterized in relation to the .alpha., .beta. and .delta. hemolysins. The sedimentation coefficient [S20,w] of the .gamma. lysin was 2.65, somewhat higher than the S20,w values of 1.4 for freshly purified alpha lysin and 1.8 for the .beta. lysin. The MW of .gamma. lysin determined by gel filtration was 45,000 daltons. The pI [isoelectric point] of .gamma. lysin was 6.0, while that of the .alpha., .beta. and .delta. lysins ranged from 8.5-9.6. The amino acid analysis of .gamma. lysin was characterized by low levels of methionine and histidine. Methionine was the N-terminus, which suggested that all of the amino acid might be involved in the N-terminal group. The .gamma. lysin was immunologically distinct from the .alpha., .beta. and .delta. lysins by quantitative precipitin tests; in Ouchterlony agar gel diffusion tests, single lines of precipitation were observed which showed no evidence of cross-reactions among the 4 hemolysins. The .gamma., .beta. and .delta. lysins had no effect in mice when injected at increasing doses ranging from 0-100 .mu.g. The .alpha. lysin killed mice, the LD50 dose being 0.68 .+-. 0.12 .mu.g, or 27-34 .mu.g/kg mouse tissue. The .gamma. lysin was lethal for guinea pigs when 50 .mu.g quantities were injected intracardially. The .gamma. lysin also lysed human leukocytes and destroyed C-6 (human lymphoblast) cells. Some N and P was released from human erythrocyte membranes treated with .gamma. lysin, when compared to untreated cells, and the rate of this release was linear over a 3 h period. The .gamma. lysin had no detectable effect on phospholipids extracted from erythrocytes or on lipid-free membrane protein. The hemolytic reaction was inhibited by erythrocyte membranes when these were added to lysin-red cell suspensions; human red cell phospholipids competitively inhibited hemolysis. Hemolysis was also inhibited by EDTA and activity could be restored by dialysis. The hemolytic reaction required Na+.