PRECURSORS OF RICIN AND RICINUS-COMMUNIS AGGLUTININ - GLYCOSYLATION AND PROCESSING DURING SYNTHESIS AND INTRACELLULAR-TRANSPORT
PRECURSORS OF RICIN AND RICINUS-COMMUNIS AGGLUTININ - GLYCOSYLATION AND PROCESSING DURING SYNTHESIS AND INTRACELLULAR-TRANSPORT
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DOI：
10.1111/j.1432-1033.1985.tb08667.x
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发表时间：
1985-01-01
期刊：
影响因子：
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通讯作者：
LORD, JM
中科院分区：
文献类型：
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作者：
LORD, JM
在体内合成过程中，蓖麻子凝集素前体最初在内质网中作为一组相对MW 64,000-68,000的核心糖基化多肽出现。用衣霉素预处理完整蓖麻子胚乳组织可部分抑制共翻译核心糖基化步骤，并导致相对分子质量为 59,000 的单一大小的未糖基化前体多肽的积累。通过与内切氨基葡萄糖苷酶 H 一起孵育，内质网中的糖基化前体被酶促转化为 59,000-MW 形式。糖基化凝集素前体从内质网向更致密的囊泡部分的细胞内转运伴随着对寡糖部分的修饰，这赋予了对内切氨基葡萄糖苷酶 H 作用的抗性。将岩藻糖添加到碳水化合物链上被认为是寡糖修饰步骤之一。岩藻糖的添加是由与表面光滑的膜部分相关的糖基转移酶催化的，该膜部分不同于内质网，暂时被鉴定为高尔基体。糖基化对于凝集素前体的细胞内运输不是必需的：在衣霉素存在下合成的未糖基化前体在蛋白体中产生未糖基化的凝集素亚基。
During synthesis in vivo the castor bean lectin precursors initially appear in the endoplasmic reticulum as a group of core glycosylated polypeptides of relative MW 64,000-68,000. Pretreatment of intact castor bean endosperm tissue with tunicamycin partially inhibits the cotranslational core glycosylation step and results in the accumulation of a single sized unglycosylated precursor polypeptide of relative molecular mass 59,000. The glycosylated precursors in the endoplasmic reticulum were enzymically converted to the 59,000-MW form by incubation with endoglucosaminidase H. Intracellular transport of the glycosylated lectin precursors from the endoplasmic reticulum to a denser vesicle fraction was accompanied by modifications to the oligosaccharide moieties which conferred resistance to the action of endoglucosaminidase H. The post-translational addition of fucose to the carbohydrate chain was identified as one of the oligosaccharide modification steps. Fucose addition was catalyzed by a glycosyltransferase associated with a smooth-surfaced membrane fraction which was distinct from the endoplasmic reticulum and which was tentatively identified as the Golgi apparatus. Glycosylation was not essential for intracellular transport of the lectin precursors: unglycosylated precursor synthesized in the presence of tunicamycin gave rise to unglycosylated lectin subunits in the protein bodies.