CELL-SURFACE AND INTRACELLULAR FUNCTIONS FOR GALACTOSE BINDING IN RICIN CYTOTOXICITY
CELL-SURFACE AND INTRACELLULAR FUNCTIONS FOR GALACTOSE BINDING IN RICIN CYTOTOXICITY
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DOI：
10.1042/bst0200734
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发表时间：
1992-11-01
影响因子：
3.9
通讯作者：
ROBERTS, LM
中科院分区：
文献类型：
--
作者：
LORD, JM;WALES, R;ROBERTS, LM
蓖麻毒蛋白是一种异源二聚体植物蛋白，对哺乳动物细胞具有强烈的细胞毒性。蓖麻毒素的两种多肽亚基在中毒过程中具有不同的作用[11]。A亚基（RTA）是一种核糖体RNA N-糖苷酶，它进入靶细胞胞质溶胶后，特异性地从28 s rRNA上去除腺嘌呤残基（大鼠肝脏28 s rRNA的情况下为A4324）[2，31]。这种特殊的腺嘌呤残基存在于28 s rRNA中高度保守的表面暴露环中，在翻译过程中对延伸因子的结合具有关键作用。含有脱嘌呤的28 s RNA的核糖体不再能够合成蛋白质。蓖麻毒素B亚基（RT B）是一种具有两个半乳糖结合位点的凝集素。这些位点与质膜糖蛋白或糖脂上存在的半乳糖苷之间的相互作用将全毒素结合到靶细胞的表面[11]。在表面结合的毒素的内吞摄取之后，B亚基被认为具有进一步的功能，
Ricin is a heterodimeric plant protein which is potently cytotoxic to mammalian cells. Both polypeptide subunits of ricin have distinct roles in the intoxication process [11. The A subunit (RTA) is a ribosomal RNA N-glycosidase which, having entered the target cell cytosol, specifically removes an adenine residue from 28s rRNA (A4324 in the case of rat liver 28s rRNA)[2, 31. This particular adenine residue, which is present in a highly conserved, surface-exposed loop in 28s rRNA, has a crucial role in the binding of elongation factors during translation. Ribosomes containing depurinated 28s RNA are no longer capable of protein synthesis. The ricin B subunit (RTB) is a lectin which has two galactose binding sites. Interaction between these sites and galactosides present on plasma membrane glycoproteins or glycolipids bind the holotoxin to the surface of target cells [11. After endocytic uptake of surface-bound toxin, the B subunit is believed to have a further function in