Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany.
Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106, Braunschweig, Germany.
Eur Biophys J. 2021 Mar;50(2):109-126. doi: 10.1007/s00249-020-01461-w. Epub 2020 Sep 19.
Gb glycosphingolipids are the specific receptors for bacterial Shiga toxin. Whereas the trisaccharidic head group of Gb defines the specificity of Shiga toxin binding, the lipophilic part composed of sphingosine and different fatty acids is suggested to determine its localization within membranes impacting membrane organisation and protein binding eventually leading to protein internalisation. While most studies use Gb extracts, chemical synthesis provides a unique tool to access different tailor-made Gb glycosphingolipids. In this review, strategies to synthesize these complex glycosphingolipids are presented. Special emphasis is put on the preparation of Gb molecules differing only in their fatty acid part (saturated, unsaturated, α-hydroxylated and both, unsaturated and α-hydroxylated). With these molecules in hand, it became possible to investigate the phase behaviour of liquid ordered/liquid disordered supported membranes doped with the Gb species by means of fluorescence and atomic force microscopy. The results clearly highlight the influence of the different fatty acids of the Gb sphingolipids on the phase behaviour and the binding properties of Shiga toxin B subunits, even though the membranes were only doped with 5 mol% of the receptor lipid. To obtain fluorescent Gb derivatives, either fatty acid labelled Gb molecules or head group labelled ones were synthesized. These molecules enabled us to address the question, where the Gb sphingolipids are localized prior protein binding by means of fluorescence microscopy on giant unilamellar vesicles. The results again demonstrate that the fatty acid of Gb plays a pivotal role for the overall membrane organisation.
Gb 糖脂是细菌志贺毒素的特异性受体。虽然 Gb 的三糖头部基团决定了志贺毒素结合的特异性，但由神经酰胺和不同脂肪酸组成的亲脂部分被认为决定了其在膜内的定位，从而影响膜的组织和蛋白质结合，最终导致蛋白质内化。虽然大多数研究使用 Gb 提取物，但化学合成提供了一种独特的工具来获得不同的定制 Gb 糖脂。在这篇综述中，介绍了合成这些复杂糖脂的策略。特别强调了制备仅在脂肪酸部分（饱和、不饱和、α-羟基化和两者，不饱和和α-羟基化）不同的 Gb 分子的策略。有了这些分子，就有可能通过荧光和原子力显微镜研究掺杂有 Gb 物种的有序/无序支持膜的相行为。结果清楚地强调了不同脂肪酸对Gb 糖脂的相行为和志贺毒素 B 亚基结合特性的影响，即使膜中仅掺杂了 5mol%的受体脂质。为了获得荧光 Gb 衍生物，合成了脂肪酸标记的 Gb 分子或头部基团标记的 Gb 分子。这些分子使我们能够通过在巨大的单层囊泡上进行荧光显微镜来解决在蛋白质结合之前 Gb 糖脂定位的问题。结果再次表明，Gb 的脂肪酸在整体膜组织中起着关键作用。
