Proline-rich cell surface antigens of horseshoe crab hemocytes are substrates for protein cross-linking with a clotting protein coagulin

Tsukasa Osaki, Nozomu Okino, Fuminori Tokunaga, Sadaaki Iwanaga, Shun Ichiro Kawabata

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Monoclonal antibodies were raised against hemocytes of the horseshoe crab Tachypleus tridentatus. All of the antibodies obtained reacted with the same protein bands on SDS-PAGE of hemocyte lysate. Flow cytometry and biotinylation of surface substances on the hemocytes indicated that the antigens are major peripheral proteins of hemocytes. The antigens were purified from hemocyte lysate and were good substrates for the horseshoe crab hemocyte transglutaminase (HcTGase). Transglutaminases play an important role during the final stage of blood coagulation in mammals and crustaceans. Although HcTGase did not intermolecularly cross-link a clottable protein coagulogen or its proteolytic product coagulin, HcTGase promoted the cross-linking of coagulin with the surface antigens, resulting in the formation of a stable polymer. We determined the nucleotide sequences for two isoproteins of the antigens. The two proteins containing 271 and 284 residues (66% identity) were composed of tandem repeats of proline-rich segments. We named them proxins-1 and -2 after proline-rich proteins for protein cross-linking. Proxins may form a stable physical barrier against invading pathogens in cooperation with hemolymph coagulation at injured sites.

Original languageEnglish
Pages (from-to)40084-40090
Number of pages7
JournalJournal of Biological Chemistry
Volume277
Issue number42
DOIs
Publication statusPublished - Oct 18 2002

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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