IDENTIFICATION OF THE LIPID MOIETY AND FURTHER CHARACTERIZATION OF THE NOVEL LIPOPHOSPHOGLYCAN-LIKE GLYCOCONJUGATES OF TRICHOMONAS-VAGINALIS AND TRICHOMONAS-FOETUS

The lipid moiety of the lipophosphoglycan (LPG)-like glycoconjugates o f Trichomonas vaginalis and Trichomonas foetus, parasites of the uroge nital tract of human and cattle, respectively, has been isolated and c haracterized by a combination of enzymatic and chemical degradation, c hromatography, and mass spectrometry. The carbohydrate composition of the glycan inositol lipid core is also reported. The glycan inositol c ore of trichomonad glycoconjugates is unique in having more than one G lcN and is significantly larger than any other glycan core reported so far. T. vaginalis glycoconjugate binds strongly to the lectin RCA-I, which suggest that the macromolecule possesses terminal beta 1,4-linke d galactosyl residues. The binding of T. foetus glycoconjugate to the lectin UEA-I suggests the presence of terminal beta 1,2-linked fucose. Acid hydrolysis of deaminated and reduced LPG products yields a [H-3] anhydromannitol-containing product, indicating the presence of unacet ylated glucosamine in the trichomonad LPGs. Reductive radiomethylation has been applied to label free amino groups in the hexosamine or othe r free amine-containing residues of the trichomonad glycoconjugates. T reatment of the LPGs with phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis liberates a ceramide substituent. Treatm ent of LPGs with nitrous acid releases a phospholipid moiety containin g myo-inositol and ceramide, implying that the LPGs are anchored in th e membrane via an inositol-phosphate-ceramide. Structural characteriza tion of the ceramide by gas-liquid chromatography (GC) and GC-mass spe ctrometry indicated the presence of the major long-chain base sphingan ine (d 18: 0 dihydrosphingosine) and a C 16:0 N-acyl group. Lipophosph oglycans from both parasites contain ceramide as their only lipid moie ty. These results suggest that T. vaginalis and T. foetus anchor their LPG-like glycoconjugates on the cell surface via inositol-phosphocera mide and also the glycan inositol core of the macromolecule appears to be unique in nature. (C) 1994 Academic Press, Inc.