Evidence of a Heparin-Binding Protein in the Plasma of the Slipper Oyster, Crassostrea iredalei

Recognition proteins play an important role in the immunodefense system of invertebrates. The haemolymph of the Slipper oyster, Crassostrea iredalei, contains a heparin-binding protein with a molecular weight of 35 kDa as determined by SDS-PAGE analysis. The protein was purified using column chromatography. This binding protein possesses a serine protease activity thus it is capable of activating the prophenoloxidase-activating (proPO) system. However, the protein lacks beta-1,3-glucanase activity. Using rabbit antiserum against the isolated protein in immunodiffusion and immunoblotting assays it produced a single precipitant and a single band, respectively. However, N-terminal amino acid sequence of BGBP: Threonine-Alanine-Arginine-Asparagine-Glutamic acid-Alanine-Asparagine-Valine was similar to Cavortin (AAT44352) and extracellular superoxide dismutase (AAY60161) from C. gigas.