Crystal structure of the GpIbα-thrombin complex essential for platelet aggregation

Direct interaction between platelet receptor glycoprotein Ibalpha (GpIbalpha) and thrombin is required for platelet aggregation and activation at sites of vascular injury. Abnormal GpIbalpha-thrombin binding is associated with many pathological conditions, including occlusive arterial thrombosis and bleeding disorders. The crystal structure of the GpIbalpha-thrombin complex at 2.6 angstrom resolution reveals simultaneous interactions of GpIbalpha with exosite I of one thrombin molecule, and with exosite II of a second thrombin molecule. In the crystal lattice, the periodic arrangement of GpIbalpha-thrombin complexes mirrors a scaffold that could serve as a driving force for tight platelet adhesion. The details of these interactions reconcile GpIbalpha-thrombin binding modes that are presently controversial, highlighting two distinct interfaces that are potential targets for development of novel antithrombotic drugs.