An arthropod cuticular chitin-binding protein endows injured sites with transglutaminase-dependent mesh

Yasuyuki Matsuda, Takumi Koshiba, Tsukasa Osaki, Haruka Suyama, Fumio Arisaka, Yoshihiro Toh, Shun Ichiro Kawabata

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


In mammals, the cornified cell envelope forms beneath the plasma membrane in epithelia and provides a vital physical barrier consisting of insoluble proteins cross-linked by transglutaminase (TGase). In the horseshoe crab Tachypleus tridentatus, TGase is stored in hemocytes and secreted in response to the simulation of bacterial lipopolysaccharides. Here we characterized a TGase substrate designated as caraxin that was identified in horseshoe crab cuticle. One of the homologs, caraxin-1, possessed a unique domain structure consisting of N- and C-terminal heptad repeats and a central domain with a tandem-repeated structure of a pentapeptide. Western blotting showed the specific localization of caraxin-1 in sub-cuticular epidermis. Moreover, we identified the pentapeptide motif to be a chitin-binding unit. Analytical ultracentrifugation revealed that caraxin-1 exists as an oligomer with 310-350 kDa, which is ∼20-mer based on the molecular mass of the monomer. The oligomers were cross-linked by TGase to form an elaborate mesh with honeycomb structures, which was electron-microscopically found to be different from the clotting mesh triggered by lipopolysaccharide-induced hemocyte exocytosis. We determined several cross-linking sites in the N- and C-terminal domains of caraxin-1. The replacements of Leu to Pro at positions 36 and 118 in caraxin-1 reduced the α-helix content, which destroyed the TGase-dependent mesh, thus indicating the importance of the N- and C-terminal domains for the proper mesh formation. In arthropods, TGase-dependent protein cross-linking may be involved in the initial stage of host defense at the sub-cuticular epidermis, as in the case of mammalian skin.

Original languageEnglish
Pages (from-to)37316-37324
Number of pages9
JournalJournal of Biological Chemistry
Issue number52
Publication statusPublished - Dec 28 2007

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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