Factor Va Residues 311–325 Represent an Activated Protein C Binding Region

Activated protein C (APC) inactivates factor Va (fVa) by proteolytically cleaving fVa heavy chain at Arg506, Arg306, and Arg679. Factor Xa (fXa) protects fVa from inactivation by APC. To test the hypothesis that fXa and APC share overlapping fVa binding sites, 15 amino acid-overlapping peptides representing the heavy chain (residues 1–709) of fVa were screened for inhibition of fVa inactivation by APC. As reported, VP311–325, a peptide...