Head-to-tail polymerization of coagulin, a clottable protein of the horseshoe crab

Hiroko Kawasaki, Takeru Nose, Tatsushi Muta, Sadaaki Iwanaga, Yasuyuki Shimohigashi, Shun Ichiro Kawabata

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32 Citations (Scopus)


A clottable protein coagulogen of the horseshoe crab Tachypleus tridentatus is proteolytically converted into an insoluble coagulin gel through non-covalent self-polymerization. Here we identified binding sites for the polymerization. A tryptic fragment, derived from the coagulin polymer chemically cross-linked by a bifunctional cross-linker, was isolated. Amino acid sequence analysis indicated that the fragment consists of two peptides cross-linked between Lys85 and Lys156. The two lysine residues are oppositely located at the head and tail regions of the elongated molecule separated by a much greater distance than the length of the cross-linker, which suggests that the cross-linking occurs intermolecularly. Based on the x-ray structural analysis, exposure of a hydrophobic cove on the head in response to the release of peptide C has been postulated (Bergner, A., Oganessyan, V., Muta, T., Iwanaga, S., Typke, D., Huber, R., and Bode, W. (1996) EMBO J. 15, 6789-6797). An octapeptide containing Tyr136, which occupies the tail end of coagulin, was found to inhibit the polymerization. Replacement of Tyr136 of the peptide with Ala resulted in loss of the inhibitory activity. These results indicated that the polymerization of coagulin proceeds through the interaction between the newly exposed hydrophobic cove on the head and the wedge-shaped hydrophobic tail.

Original languageEnglish
Pages (from-to)35297-35301
Number of pages5
JournalJournal of Biological Chemistry
Issue number45
Publication statusPublished - 2000 Nov 10

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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