A Clottable Protein (Coagulogen) of Horseshoe Crab Hemocytes. Structural Change of Its Polypeptide Chain during Gel Formation1

A clottable protein (coagulogen) isolated from a hemocyte lysate of the Japanese horseshoe crab (Tachypleus tridentatus) was incubated with an endotoxin-activated clotting enzyme(s) partially purified from the same lysate, and its structural change during gel formation was examined. The results indicated that the enzymatic formation of gel involved limited proteolysis of the $Arg46-Gly47$ and $Arg18-Thr19$linkages located in the N-terminal portion of the coagulogen, liberating peptide C.