The effect of thiol-active compounds and sterols on the membrane-associated hemolysin of Mycoplasma pulmonis.

Previous studies had shown that Mycoplasma pulmonis contained a bovine serum albumin-dependent, membrane-associated hemolysin. Biochemical analyses were performed to further characterize this activity. The membrane-associated hemolytic activity could be activated by dithiothreitol and beta-mercaptoethanol, and inactivated by oxidizing compounds, a sulfhydryl inhibitor and heat treatment. Cholesterol and other sterols were inhibitory in a stereo-specific manner, but they did not interfere with adherence of M. pulmonis to red blood cells. These results indicated that once attached, the M. pulmonis hemolysin recognized cholesterol in the opposing membrane leading to red cell lysis. Because of the unique location of this toxin and its sensitivity to cholesterol, the mycoplasma membrane hemolysins may belong to a unique class of bacterial toxins.