A family of glycolipids from Toxoplasma gondii. Identification of candidate glycolipid precursor(s) for Toxoplasma gondii glycosylphosphatidylinositol membrane anchors.

Four major glycolipids were extracted from Toxoplasma gondii tachyzoites which were metabolically labeled with tritiated glucosamine, mannose, palmitic and myristic acid, ethanolamine, and inositol. Judging from their sensitivity to a set of enzymatic and chemical tests, these glycolipids share the following properties with the glycolipid moiety of the glycosylphosphatidylinositol anchor (GPI anchor) of the major surface protein, P30, of T. gondii: 1) a nonacetylated glucosamine-inositol phosphate linkage; 2) sensitivity toward phosphatidylinositol-specific phospholipase C and nitrous acid; 3) identity of HF-dephosphorylated GPI glycan backbone between three glycolipids and the HF-dephosphorylated core glycan of the GPI anchor of the major surface protein P30; 4) the presence of a linear core glycan structure blocked by an ethanolamine phosphate residue(s). Taken together with the nature of radiolabeled precursors incorporated into these glycolipids, the data indicate that these GPIs are involved in the biosynthesis of the GPI-membrane anchors of T. gondii.