Tachylectin-2: Crystal structure of a specific GlcNAc/GalNAc-binding lectin involved in the innate immunity host defense of the Japanese horseshoe crab Tachypleus tridentatus

Hans Georg Beisel, Shun Ichiro Kawabata, Sadaaki Iwanaga, Robert Huber, Wolfram Bode

Research output: Contribution to journalArticle

134 Citations (Scopus)

Abstract

Tachylectin-2, isolated from large granules of the hemocytes of the Japanese horseshoe crab (Tachypleus tridentatus), is a 236 amino acid protein belonging to the lectins. It binds specifically to N-acetylglucosamine and N-acetylgalactosamine and is a part of the innate immunity host defense system of the horseshoe crab. The X-ray structure of tachylectin-2 was solved at 2.0 Å resolution by the multiple isomorphous replacement method and this molecular model was employed to solve the X-ray structure of the complex with N-acetylglucosamine. Tachylectin-2 is the first protein displaying a five-bladed β-propeller structure. Five four-stranded antiparallel β-sheets of W-like topology are arranged around a central water-filled tunnel, with the water molecules arranged as a pentagonal dodecahedron. Tachylectin-2 exhibits five virtually identical binding sites, one in each β-sheet. The binding sites are located between adjacent β-sheets and are made by a large loop between the outermost strands of the β-sheets and the connecting segment from the previous β-sheet. The high number of five binding sites within the single polypeptide chain strongly suggests the recognition of carbohydrate surface structures of pathogens with a fairly high ligand density. Thus, tachylectin-2 employs strict specificity for certain N-acetyl sugars as well as the surface ligand density for self/non-self recognition.

Original languageEnglish
Pages (from-to)2313-2322
Number of pages10
JournalEMBO Journal
Volume18
Issue number9
DOIs
Publication statusPublished - May 4 1999

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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