Ultrastructural analysis of toxin binding and entry into mammalian cells
Ultrastructural analysis of toxin binding and entry into mammalian cells
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毒素结合和进入哺乳动物细胞的超微结构分析
作者：
G. Nicolson
极低浓度的植物毒素可以杀死哺乳动物细胞，其中一些，如蓖麻毒蛋白和相思豆毒蛋白，从蓖麻和相思子中分离出来，据报道，抑制蛋白质合成细胞1 -3和无细胞系统4，5。蓖麻毒素通过催化灭活核糖体的60 S亚基5 -7抑制肽链延伸。它是一种半乳糖结合糖蛋白，分子量为60，000，含有两个通过二硫桥连接的不同亚基8 -11，似乎与凝集素R相同。通过亲和层析分离的communis凝集素II（RCAII）8 -12。蓖麻毒素或RCAII已被用于抑制体内腹水肿瘤细胞的生长13，并作为含有末端D-半乳糖或N-乙酰基-D-半乳糖胺样糖的寡糖受体14 -17的细胞表面探针11，14，18，19。我发现RCAII通过内吞作用进入哺乳动物细胞（类似于奥利弗等人20的发现），然后释放到细胞质中，在那里它显然直接作用于蛋白质合成。
VERY low concentrations of phytotoxins can kill mammalian cells, and some of them, such as ricin and abrin, isolated from Ricinus communis and Abrus precatorius, have been reported to suppress protein synthesis in cells1–3 and cell-free systems4,5. Ricin inhibits peptide chain elongation by catalytically inactivating the 60S subunits of ribosomes5–7. It is a galactosebinding glycoprotein of molecular weight 60,000, containing two nonidentical subunits linked by disulphide bridges8–11 and seems to be identical to the lectin R. communis agglutinin II (RCAII) isolated by affinity chromatography8–12. Ricin, or RCAII, has been used to suppress the growth of ascites tumour cells in vivo13, and as a cell surface probe for oligosaccharide receptors14–17 containing terminal D-galactose or N-acetyl-D-galactosamine-like saccharides11,14,18,19. I have found that RCAII enters mammalian cells by endocytosis (similar to the findings of Oliver et al.20) and is then released into the cytoplasm, where it apparently acts directly on protein synthesis.