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 (PubMed:19913916). 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 (PubMed:23754290, PubMed:28193526). Interacts with human receptor CXCR4 and specifically inhibits CXCL12-induced calcium mobilization and cell migration (PubMed:19308288). Interacts with prothrombin/F2 and coagulation factor X/F12 (PubMed:23754290, PubMed:28193526). Interacts with human CXCR4 (PubMed:19308288). Belongs to the staphylococcal/streptococcal toxin family.