Utsumi T, Aizono Y, Funatsu G
FEBS Lett. 1987 May 25;216(1):99-103. doi: 10.1016/0014-5793(87)80764-0.
The interaction of ricin with ganglioside GM1 or glycoprotein containing liposomes was investigated. At neutral pH, ricin bound to galactose moieties on the surface of the liposomes to form ricin-liposomes complexes, but did not associate with their lipid bilayers. When these ricin-liposomes complexes were exposed to a pH below 5, ricin bound to GM1-liposomes became associated with the lipid bilayer, whereas ricin bound to glycoprotein-liposomes (containing human erythrocyte Band 3) was only rarely associated. Association of ricin with the lipid bilayer of GM1-liposomes did not occur in the presence of lactose, which inhibits the binding of ricin to ganglioside GM1. Using a hydrophobic probe, 8-amino-1-naphthalene sulfonic acid (ANS), it was revealed that an acidity below pH 5 resulted in exposure of hydrophobic regions on the ricin molecule. These results strongly suggest that association of ricin with the lipid bilayer of GM1-liposomes at acidic pH is mediated by the binding of ricin to ganglioside GM1 at neutral pH and occurs through interaction between the exposed hydrophobic region on the ricin molecule and the lipid bilayer of GM1-liposomes at low pH.
研究了蓖麻毒素与神经节苷脂GM1或含糖蛋白脂质体的相互作用。在中性pH值下，蓖麻毒素与脂质体表面的半乳糖部分结合形成蓖麻毒素-脂质体复合物，但不与它们的脂质双层结合。当这些蓖麻毒素-脂质体复合物暴露于pH值低于5的环境时，与GM1-脂质体结合的蓖麻毒素会与脂质双层结合，而与糖蛋白-脂质体（含人红细胞带3）结合的蓖麻毒素很少结合。在乳糖存在的情况下，蓖麻毒素不会与GM1-脂质体的脂质双层结合，乳糖会抑制蓖麻毒素与神经节苷脂GM1的结合。使用疏水探针8-氨基-1-萘磺酸（ANS）发现，pH值低于5时会导致蓖麻毒素分子上的疏水区域暴露。这些结果有力地表明，酸性pH值下蓖麻毒素与GM1-脂质体脂质双层的结合是由中性pH值下蓖麻毒素与神经节苷脂GM1的结合介导的，并且是通过低pH值下蓖麻毒素分子上暴露的疏水区域与GM1-脂质体脂质双层之间的相互作用发生的。
