Azzouz N, Striepen B, Gerold P, Capdeville Y, Schwarz R T
Zentrum für Hygiene und Medizinische Mikrobiologie, Phillips-Universität Marburg, Germany.
EMBO J. 1995 Sep 15;14(18):4422-33. doi: 10.1002/j.1460-2075.1995.tb00121.x.
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.
在由自由生活的原生动物双小核草履虫制备的无细胞系统中合成的糖脂，分别使用GDP-[3H]甘露糖和UDP-[3H]N-乙酰葡糖胺用[3H]甘露糖和[3H]葡糖胺进行标记，被鉴定并在结构上表征为糖基肌醇磷酸神经酰胺（GIP-神经酰胺）。在双小核草履虫156株的G表面抗原的GIP膜锚中也发现了基于神经酰胺的脂质。通过结合使用GDP-[3H]甘露糖的体外标记和33P的体内标记，我们发现双小核草履虫GIP-神经酰胺的核心聚糖被鉴定为甘露糖基磷酸的酸不稳定修饰所取代。甘露糖基磷酸对糖基肌醇磷脂核心聚糖的修饰在其他生物体中迄今尚未见报道。通过脉冲追踪分析研究了双小核草履虫中GIP-神经酰胺中间体的生物合成。报道了它们的结构表征。我们提出了双小核草履虫表面蛋白假定的GIP-神经酰胺膜锚前体的以下结构：磷酸乙醇胺-6Man-α1-2Man-α1-6Man-（甘露糖基磷酸）-α1-4葡糖胺-肌醇-磷酸神经酰胺。
