Cheng, X. J., Hughes, M. A., Huston, C. D., Loftus, B., Gilchrist, C. A., Lockhart, L. A., Ghosh, S., Miller-Sims, V., Mann, B. J., Petri, W. A., Jr., Tachibana, H.
Intermediate Subunit of the Gal/GalNAc Lectin of Entamoeba histolytica Is a Member of a Gene Family Containing Multiple CXXC Sequence Motifs
Infect Immun. 2001 Sep 01; 69(9): 5892-8.
Killing by Entamoeba histolytica requires parasite adherence to host galactose- and N-acetyl-D-galactosamine (Gal/GalNAc)-containing cell surface receptors. A 260-kDa heterodimeric E. histolytica Gal/GalNAc lectin composed of heavy (Hgl) and light (Lgl) subunits has been previously described. Here we present the cloning and characterization of Igl, a 150-kDa intermediate subunit of the Gal/GalNAc lectin. Igl, Hgl, and Lgl colocalized on the surface membrane of trophozoites. Two unlinked copies of genes encoding Igl shared 81% amino acid sequence identity (GenBank accession no. AF337950 and AF337951). They encoded cysteine-rich proteins with amino- and carboxy-terminal hydrophobic signal sequences characteristic of glycosylphosphatidylinositol (GPI)-anchored membrane proteins. The igl genes lacked carbohydrate recognition domains but were members of a large family of amebic genes containing CXXC and CXC motifs. These data indicate that Igl is part of the parasite's multimolecular Gal/GalNAc adhesin required for host interaction.