Galactose recognition by the apicomplexan parasite Toxoplasma gondii

J Biol Chem. 2012 May 11;287(20):16720-33. doi: 10.1074/jbc.M111.325928. Epub 2012 Mar 7.


Toxosplasma gondii is the model parasite of the phylum Apicomplexa, which contains numerous obligate intracellular parasites of medical and veterinary importance, including Eimeria, Sarcocystis, Cryptosporidium, Cyclospora, and Plasmodium species. Members of this phylum actively enter host cells by a multistep process with the help of microneme protein (MIC) complexes that play important roles in motility, host cell attachment, moving junction formation, and invasion. T. gondii (Tg)MIC1-4-6 complex is the most extensively investigated microneme complex, which contributes to host cell recognition and attachment via the action of TgMIC1, a sialic acid-binding adhesin. Here, we report the structure of TgMIC4 and reveal its carbohydrate-binding specificity to a variety of galactose-containing carbohydrate ligands. The lectin is composed of six apple domains in which the fifth domain displays a potent galactose-binding activity, and which is cleaved from the complex during parasite invasion. We propose that galactose recognition by TgMIC4 may compromise host protection from galectin-mediated activation of the host immune system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Adhesion Molecules
  • Galactose / immunology
  • Galactose / metabolism*
  • Galectins / chemistry
  • Galectins / genetics
  • Galectins / immunology
  • Galectins / metabolism*
  • Humans
  • Multiprotein Complexes / chemistry
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / immunology
  • Multiprotein Complexes / metabolism*
  • Protein Structure, Tertiary
  • Protozoan Proteins
  • Toxoplasma / chemistry
  • Toxoplasma / genetics
  • Toxoplasma / immunology
  • Toxoplasma / metabolism*
  • Toxoplasmosis / genetics
  • Toxoplasmosis / immunology
  • Toxoplasmosis / metabolism


  • Cell Adhesion Molecules
  • Galectins
  • MIC4 protein, Toxoplasma gondii
  • Multiprotein Complexes
  • Protozoan Proteins
  • Galactose

Associated data

  • PDB/2LL3
  • PDB/2LL4
  • PDB/4A5V