Inactivation of gamma-hemolysin H gamma II component by addition of monosialoganglioside GM1 to human erythrocyte.

The Staphylococcal toxins leukocidin and gamma-hemolysin consist of two protein components: F and S in leukocidin and H gamma I and H gamma II in gamma-hemolysin. The two toxins share one component (F = H gamma I). We found that the H gamma II component was completely inactivated by the addition of monosialoganglioside GM1 at the molar ratio of 1:1. Disialogangliosides GD1a and GD1b had little effect on the inactivation of H gamma II. The molar ratios of GD1a and GD1b to H gamma II needed for maximum inactivation were 30:1 and 100:1, respectively. Related glycolipids caused little if any inactivation. H gamma II bound to GM1 to form H gamma II-GM1 complexes. Analysis of the intrinsic aromatic amino acid fluorescence in H gamma II and H gamma II-GM1 with 280 nm as the excitation wavelength showed that GM1 in the complex reduced the fluorescence intensity of H gamma II by 12% without changing the wavelength of maximum emission (325 nm). We concluded that GM1 is a receptor of the H gamma II component on human erythrocytes and that H gamma II takes on a different conformation when it binds to GM1.