Severe aortic valve stenosis can induce inappropriate cleavage of this protein, resulting in gastrointestinal AVM and an acquired form of a namesake disorder in Heyde’s syndrome. This protein is degraded by the metalloenzyme ADAMTS13, inhibition of which results in ultra-large multimers of this protein causing TTP. In the RIPA test for its namesake disease, adding ristocetin to patient samples mimics the high shear stress needed to expose the (*) GpIb (“G-P-one-B”) binding site of this glycoprotein. This large protein is released from Weibel–Palade bodies in the endothelium and from alpha granules. This protein shields and transports Factor VIII (“eight”), and it binds to both collagen and platelets to facilitate coagulation. For 10 points, the most common inherited bleeding disorder is caused (10[1])by a deficiency in which eponymously-named clotting factor? ■END■