Popoli M, Paterno R
Laboratory of Neurochemistry, School of Medicine, Napoli, Italy.
Neuroreport. 1991 Feb;2(2):93-5. doi: 10.1097/00001756-199102000-00007.
Synaptic vesicles contain a protein (agglutinin) which binds cell plasma membranes. The protein activity is titrated measuring the agglutination of rabbit trypsinized-fixed red blood cells induced by serial dilutions of purified vesicles. The protein is highly concentrated in vesicles: the specific activity is 150-fold higher in vesicles compared to the brain homogenate, and 20-fold higher compared to the crude synaptosomal membrane fraction. The binding is specifically inhibited by the four major brain sialoglycosphingolipids, with a higher affinity for polysialo- rather than for monosialoganglioside (GM1) IC50 are 3.9 x 10(-5) M (GT1b), 8.9 x 10(-5) M (GD1a), 2.8 x 10(-4) M (GD1b) and 4.9 x 10(-4) M (GM1). Cells which are not agglutinated by the vesicles (human red blood cells) can be activated by incubation with gangliosides: insertion of the glycolipids in the plasma membranes makes them sensitive to the vesicle haemagglutinin.
突触小泡含有一种能结合细胞质膜的蛋白质（凝集素）。通过测量经纯化小泡系列稀释诱导的兔胰蛋白酶处理固定红细胞的凝集来滴定该蛋白质活性。该蛋白质在小泡中高度浓缩：与脑匀浆相比，小泡中的比活性高150倍，与粗制突触体膜部分相比高20倍。四种主要的脑唾液酸糖鞘脂可特异性抑制这种结合，对多唾液酸糖鞘脂的亲和力高于对单唾液酸神经节苷脂（GM1）的亲和力，IC50分别为3.9×10⁻⁵M（GT1b）、8.9×10⁻⁵M（GD1a）、2.8×10⁻⁴M（GD1b）和4.9×10⁻⁴M（GM1）。不被小泡凝集的细胞（人类红细胞）可通过与神经节苷脂孵育而被激活：糖脂插入质膜使其对小泡血凝素敏感。
