Jararhagin and jaracetin: Novel snake venom inhibitors of the integrin collagen receptor, α₂β₁

Two novel proteins, jararhagin and jaracetin, were purified from Bothrops jararaca viper venom. Jararhagin is a 55-kDa member of the metalloprotease-disintegrin family. Jaracetin is a 60-kDa dimer representing a differently processed form of jararhagin. Like botrocetin, a previously described viper venom protein, jararhagin and jaracetin modulated binding of von Willebrand Factor to the glycoprotein Ib-IX complex on platelets through a specific interaction with the von Willebrand Factor A1 domain. Both jararhagin and jaracetin, but not botrocetin, also blocked α₂β₁-dependent platelet adhesion to collagen, a receptor interaction mediated through a homologous A domain on the integrin α₂ subunit.