Canine protein C was not a single-chain polypeptide. Western blot of 12% SDS-PAGE using GMA-093 (which targets the heavy chain of human protein C) depicting CnPC purified from canine plasma by salt precipitation and immunoaffinity chromatography. Lane 1: Unbound protein fraction from immunoaffinity chromatography did not contain protein C. Lane 2: Five μg of non-reduced CnPC purified from canine plasma. Immunoreactivity was detected at ~75 kDa. Lane 3: Five μg of reduced CnPC purified from canine plasma. Immunoreactivity was detected at ~49 kDa due to dissociation from the light chain.