Glycosylinositol-phosphoceramide in the free-living protozoan Paramecium primaurelia: modification of core glycans by mannosyl phosphate.
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.
Azzouz
N
N
Zentrum für Hygiene und Medizinische Mikrobiologie, Phillips-Universität Marburg, Germany.
Striepen
B
B
Gerold
P
P
Capdeville
Y
Y
Schwarz
R T
RT
D000818:Animals; D002240:Carbohydrate Sequence; D002474:Cell-Free System; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D005944:Glucosamine / Q000378:metabolism; D006017:Glycolipids / Q000096:biosynthesis; D006028:Glycosphingolipids / Q000096:biosynthesis / Q000737:chemistry*; D008358:Mannose / Q000378:metabolism; D008360:Mannosephosphates / Q000032:analysis*; D008362:Mannosides / Q000737:chemistry*; D008969:Molecular Sequence Data; D010247:Paramecium / Q000737:chemistry*
D006017:Glycolipids; D006028:Glycosphingolipids; D008360:Mannosephosphates; D008362:Mannosides; D005944:Glucosamine; D008358:Mannose