Morino H, Sakakibara R, Ishiguro M
Department of Biochemistry, Nagasaki University, Japan.
Biol Pharm Bull. 1995 Dec;18(12):1770-2. doi: 10.1248/bpb.18.1770.
Ricin toxin is a toxic glycoprotein comprising two polypeptide chains, A and B, joined by a disulfide bond. The binding of its B-chain to the cell surface glycoconjugate having non-reducing terminal galactose (ricin receptors) has been assumed to allow the internalization of ricin into the cell, followed by the release of the free A-chain into cytosol, which then inhibits cellular protein synthesis in eukaryotic cells (cytotoxic effect). In order to investigate whether the binding of ricin to its receptors is essential to the expression of its toxicity, ricin was allowed to be incorporated into the cells using liposome encapsulated ricin (ricin-encapsulated liposomes). Protein synthesis in cultured Hela cells was inhibited by incubation not only with intact ricin but also with ricin-encapsulated liposomes, indicating that the binding of ricin to its receptor is not required for the expression of its toxicity.
蓖麻毒素是一种有毒糖蛋白，由通过二硫键连接的两条多肽链A和B组成。其B链与具有非还原末端半乳糖的细胞表面糖缀合物（蓖麻毒素受体）的结合被认为可使蓖麻毒素内化进入细胞，随后游离的A链释放到细胞质中，进而抑制真核细胞中的细胞蛋白质合成（细胞毒性作用）。为了研究蓖麻毒素与其受体的结合对其毒性表达是否至关重要，使用脂质体包裹的蓖麻毒素（蓖麻毒素包裹的脂质体）使蓖麻毒素掺入细胞中。不仅完整的蓖麻毒素，而且蓖麻毒素包裹的脂质体孵育均可抑制培养的Hela细胞中的蛋白质合成，这表明蓖麻毒素与其受体的结合对其毒性表达并非必需。
