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Glycosylinositol‐phosphoceramide in the free‐living protozoan Paramecium primaurelia: modification of core glycans by mannosyl phosphate.
Author(s) -
Azzouz N.,
Striepen B.,
Gerold P.,
Capdeville Y.,
Schwarz R. T.
Publication year - 1995
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1995.tb00121.x
Subject(s) - potpourri , hygiene , library science , biology , medicine , computer science , botany , pathology
Glycolipids synthesized in a cell‐free system prepared from the free‐living protozoan Paramecium primaurelia and labelled with [3H]mannose and [3H]glucosamine using GDP‐[3H]mannose and UDP‐[3H]N‐acetyl glucosamine, respectively, were identified and structurally characterized as glycosylinositol‐phosphoceramides (GIP‐ceramides). The ceramide‐based lipid was also found in the GIP membrane anchor of the G surface antigen of P.primaurelia, strain 156. Using a combination of in vitro labelling with GDP‐[3H]mannose and in vivo labelling with 33P, we found that the core glycans of the P.primaurelia GIP‐ceramides were substituted with an acid‐labile modification identified as mannosyl phosphate. The modification of the glycosylinositol‐phospholipid core glycan by mannosyl phosphate has not been described to date in other organisms. The biosynthesis of GIP‐ceramide intermediates in P.primaurelia was studied by a pulse‐chase analysis. Their structural characterization is reported. We propose the following structure for the putative GIP‐ceramide membrane anchor precursor of P.primaurelia surface proteins: ethanolamine phosphate‐6Man‐alpha 1–2Man‐alpha 1–6Man‐(mannosyl phosphate)‐alpha 1–4glucosamine‐inositol‐phosphoceramide.