Björkholm Patrik, Ernst Andreas M, Hacke Moritz, Wieland Felix, Brügger Britta, von Heijne Gunnar
Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden.
Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
Biochim Biophys Acta. 2014 Aug;1838(8):2066-70. doi: 10.1016/j.bbamem.2014.04.026. Epub 2014 May 2.
Specific interactions between transmembrane proteins and sphingolipids is a poorly understood phenomenon, and only a couple of instances have been identified. The best characterized example is the sphingolipid-binding motif VXXTLXXIY found in the transmembrane helix of the vesicular transport protein p24. Here, we have used a simple motif-probability algorithm (MOPRO) to identify proteins that contain putative sphingolipid-binding motifs in a dataset comprising proteomes from mammalian organisms. From these motif-containing candidate proteins, four with different numbers of transmembrane helices were selected for experimental study: i) major histocompatibility complex II Q alpha chain subtype (DQA1), ii) GPI-attachment protein 1 (GAA1), iii) tetraspanin-7 TSN7, and iv), metabotropic glutamate receptor 2 (GRM2). These candidates were subjected to photo-affinity labeling using radiolabeled sphingolipids, confirming all four candidate proteins as sphingolipid-binding proteins. The sphingolipid-binding motifs are enriched in the 7TM family of G-protein coupled receptors, predominantly in transmembrane helix 6. The ability of the motif-containing candidate proteins to bind sphingolipids with high specificity opens new perspectives on their respective regulation and function.
跨膜蛋白与鞘脂之间的特异性相互作用是一种了解甚少的现象，仅发现了少数几个实例。最具特征的例子是在囊泡运输蛋白p24的跨膜螺旋中发现的鞘脂结合基序VXXTLXXIY。在此，我们使用了一种简单的基序概率算法（MOPRO），在一个包含哺乳动物生物体蛋白质组的数据集里识别含有假定鞘脂结合基序的蛋白质。从这些含有基序的候选蛋白质中，选择了四个具有不同跨膜螺旋数量的进行实验研究：i）主要组织相容性复合体II Qα链亚型（DQA1），ii）糖基磷脂酰肌醇附着蛋白1（GAA1），iii）四跨膜蛋白-7（TSN7），以及iv）代谢型谷氨酸受体2（GRM2）。使用放射性标记的鞘脂对这些候选蛋白进行光亲和标记，证实这四种候选蛋白均为鞘脂结合蛋白。鞘脂结合基序在G蛋白偶联受体的7TM家族中富集，主要在跨膜螺旋6中。含有基序的候选蛋白以高特异性结合鞘脂的能力为它们各自的调节和功能开辟了新的视角。
