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Protein Domain : IPR000275

Description  Coagulogen is a gel-forming protein of hemolymph that hinders the spread of invaders by immobilising them [ , ]. The protein contains a single 175- residue polypeptide chain; this is cleaved after Arg-18 and Arg-46 by a clotting enzyme contained in the hemocyte and activated by a bacterial endotoxin (lipopolysaccharide). Cleavage releases two chains of coagulin, A and B, linked by two disulphide bonds, together with the peptide C [, ]. Gel formation results from interlinking of coagulin molecules. The crystal structure of a coagulogen has been revealed. Coagulogen contains a C-terminal domain that has a NGF-like fold [].Mammalian blood coagulation is based on the proteolytically induced polymerisation of fibrinogens. Initially, fibrin monomers noncovalently interact with each other. The resulting homopolymers are further stabilised when the plasma transglutaminase (TGase) intermolecularly cross-links epsilon-(gamma-glutamyl)lysine bonds. In crustaceans, hemolymph coagulation depends on the TGase-mediated cross-linking of specific plasma-clotting proteins, but without the proteolytic cascade. In horseshoe crabs, the proteolytic coagulation cascade triggered by lipopolysaccharides and beta-1,3-glucans leads to the conversion of coagulogen into coagulin, resulting in noncovalent coagulin homopolymers through head-to-tail interaction. Horseshoe crab TGase, however, does not cross-link coagulins intermolecularly. It has been shown that coagulins are cross-linked on hemocyte cell surface proteins called proxins. This indicates that a cross-linking reaction at the final stage of hemolymph coagulation is an important innate immune system of horseshoe crabs [ ]. Name  Coagulin
Short Name  Coagulin Type  Family
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Genomics

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