Serum carbohydrate-binding IgM are present in Vietnamese striped catfish (Pangasianodon hypophthalmus) but not in North African catfish (Clarias gariepinus).

Giang Duong Thi Huong, Edilbert Van Driessche, Sonia Beeckmans

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Pangasianodon hypophthalmus serum was fractionated by affinity chromatography on 12 different Sepharose-carbohydrate columns and proteins eluted by the corresponding sugar. Binding to the affinity matrices is dependent on Ca2+ ions. Upon gel filtration using Superose-12, essentially one fraction was obtained, eluting as a protein with a molecular mass of about 900 kDa. SDS-PAGE in reducing conditions revealed the presence of large (72 kDa) subunits (H-chains) and one up to three small (24, 26 and/or 28-29 kDa) subunits (L-chains). The isolated proteins were shown to be IgM since they bind monoclonal anti-P. hypophthalmus IgM antibodies. Rabbit polyclonal anti-galactose-binding IgM only cross-react with some sugar-binding IgM. The H-chains of the anti-carbohydrate IgM are glycosylated. Circular dichroism studies revealed that the IgMs have an ''all-beta'' type of structure, and that Ca2+ ions, though essential for carbohydrate-binding activity, are not required for the structural integrity of the molecules. In nonreducing SDS-PAGE, only monomers and halfmers were obtained, showing that there are no disulfide bonds linking the monomers, and that a disulfide bond connecting both H-chains within one monomer is only present in 45% of the molecules. Both the monomers and the halfmers display molecular mass heterogeneity which is indicative for redox forms at the level of the intradomain disulfide bonds. The native carbohydrate-binding IgMs agglutinate erythrocytes from different animals, as well as fish pathogenic bacteria. Similar proteins could not be isolated from another catfish, Clarias gariepinus.
Original languageEnglish
Pages (from-to)418-432
Number of pages15
JournalDevelopmental and Comparative Immunology
Volume36
Publication statusPublished - Feb 2012

Keywords

  • Vietnamese striped catfish
  • Pangasianodon hypophthalmus
  • Carbohydrate-binding IgM
  • Redox forms
  • Cross-reactivity
  • Aeromonas hydrophila agglutination
  • Edwardsiella ictaluri agglutination

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