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Structural analysis of glycosyl‐phosphatidylinositol membrane anchor of the Toxoplasma gondii tachyzoite surface glycoprotein gp23
Author(s) -
Tomavo Stanislas,
Dubremetz JeanFrancois,
Schwarz Ralph T.
Publication year - 1993
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(93)90126-y
Subject(s) - biology , biochemistry , mannose , phosphatidylinositol , phospholipase c , glycan , glucosamine , inositol , glycoprotein , microbiology and biotechnology , enzyme , kinase , receptor
Summary— In this study we describe the biochemical features of the Toxoplasma gondii tachyzoite surface glycoprotein, gp23, demonstrating that it is attached to the parasite membrane by a glycosyl‐phosphatidyl inositol anchor. Gp23 was metabolically labeled with tritiated palmitate, myristate, ethanolamine, inositol, glucosamine, mannose and galactose, as expected for a GPI‐anchor structure. Gp23 was released from the surface of living parasites after treatment with phosphatidyl inositol‐specific phospholipase C (PI‐PLC) and the resulting water‐soluble protein was immunoprecipitated with a monoclonal antibody specific for gp23. The GPIcore glycan was generated after aqueous‐HF dephosphorylation followed by nitrous acid deamination and its carbohydrate structure was analyzed using selective exo‐ and endoglycosidase treatments. Finally, the phosphatidylinositol moiety of gp23 was characterized using PI‐PLC and phospholipase A 2 (PLA 2 ) digestions. Our cumulative data suggest that gp23 of T gondii tachyzoites contains a modified GPI‐backbone similar to the mammalian Thy‐1 anchor, consisting of a conserved core structure (ethanolaminePO 4 ‐6‐Manαl‐2‐Manαl‐6‐Manαl‐4‐GIcNαl‐6‐PI) bearing β‐linked N‐acetylgalactosamine residue(s).