Protein C is a Vitamin K-dependent plasma zymogen that is activated by proteolytic cleavage of the thrombin-thrombomodulin complex to form an anticoagulant enzyme. Anti-Protein C mouse monoclonal antibody (clone HPC4) binds specifically to an epitope sequence spanning the thrombin cleavage site of protein C and is immobilized. Anti-Protein C recognizes the 12-amino acid sequence (EDQVDPRLIDGK), which encodes residues 6 through 17 of the heavy chain of Protein C. The formation of the Anti-Protein C/protein C epitope complex is dependent on the presence of calcium ions. In the presence of Ca2+, the antibody binds with high affinity and specificity to this sequence in native human Protein C or in proteins tagged with this epitope. This efficient binding within the recombinant fusion protein occurs regardless of the site of incorporation of the epitope tag (i.e., N terminus, C terminus, or within the reading frame). This unique antibody is especially well suited for purification of recombinant fusion proteins tagged with the protein C epitope.