Plays a role in the inhibition of host complement activation via the classical pathway by interacting with the Fc region of human IgG and thereby interfering with the IgG/C1q interaction. Inhibits also the penultimate step of plasma clotting by interacting with prothrombin/F2 and coagulation factor X/F12. Does not affect the protease activity of thrombin but interferes with the conversion of prothrombin to thrombin. Interacts with human receptor CXCR4 and specifically inhibits CXCL12-induced calcium mobilization and cell migration. Interacts with prothrombin/F2 and coagulation factor X/F12. Interacts with human CXCR4. Belongs to the staphylococcal/streptococcal toxin family.