AGGLUTINATION ACTIVITY OF LIMULUS-POLYPHEMUS COAGULOGEN FOLLOWING LIMITED PROTEOLYSIS

1. A 14 kDa protein with cell agglutination properties has been purifi ed from endotoxin-activated L. polyphemus amebocyte lysate. Amino term inal sequence analysis indicates that this protein corresponds to a pr oteolytically cleaved product (coagulin) of coagulogen. 2. Similar cel l agglutination activity can be generated, in vitro, by proteolytic cl eavage of the coagulogen with either trypsin, endogenous protease or a n alpha2M/enzyme complex isolated from amebocytes. 3. Studies with [I- 125]-labeled coagulogen showed that only coagulin, not the intact coag ulogen, binds to rabbit erythrocytes and formalin-fixed amebocytes.4. The cell agglutination activity of coagulin towards erythrocytes was n ot inhibited by various sugars tested, and was not Ca2+-dependent. 5. These findings suggest that coagulogen and coagulin are reminiscent of their mammalian counterparts, fibrinogen and fibrin, in their clottin g and relative adhesive properties.