Heat stability and species range of purified staphylococcal alpha-toxin.

Cooper, Louis Z. (New England Medical Center Hospital, Boston, Mass.), Morton A. Madoff, and Louis Weinstein. Heat stability and species range of purified staphylococcal alpha-toxin. J. Bacteriol. 91:1686-1692. 1966.-Heating of high-titer purified staphylococcal alpha-toxin at 60 and 80 C resulted in a double-sloped curve of inactivation of the hemolytic effect on rabbit erythrocytes. Early inactivation was less at the lower temperature, but activity persisted for a longer time at 80 C. Toxin inactivated at 60 C showed renewed activity when heated briefly at 80 C. A precipitate which formed during heating of alpha-toxin at 60 or 80 C yielded hemolytic activity when resuspended and heated at 80 but not at 60 C. Supernatant fluid of heat-precipitated toxin was heat-labile and did not regain activity when heated at 80 C. The results indicate that the "paradoxical effect" of heating of staphylococcal alpha-toxin is not due to a thermolabile inhibitor, but results from alteration of the toxin molecule to a heat-stable active form. Demonstration of renewed activity by 80 C heating of purified toxin requires potent toxin preparations and brief heating periods. Hemolysis of erythrocytes of several animal species by purified alpha-toxin was generally similar to that produced by impure toxin. Rabbit cells were most susceptible. Human and horse erythrocytes hemolyzed to less than 0.1% of the extent of rabbit cells. Blood cells of other species were intermediate in their response to the lytic effect of alpha-toxin.