Transient N-acetylglucosamine in the biosynthesis of phytohemagglutinin: attachment in the Golgi apparatus and removal in protein bodies.
Transient N-acetylglucosamine in the biosynthesis of phytohemagglutinin: attachment in the Golgi apparatus and removal in protein bodies.
复制标题
植物凝集素的生物合成中的瞬时N-乙酰葡萄糖：高尔基体中的附着和蛋白质体中的去除。
DOI：
10.1083/jcb.99.1.133
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发表时间：
1984-07
影响因子：
7.8
通讯作者：
Chrispeels, M J
中科院分区：
文献类型：
--
作者：
Vitale, A;Chrispeels, M J
普通菜豆（Phaseolus vulgaris L.）在种子发育过程中合成大量的凝集素植物血凝素（PHA）。PHA的多肽由内质网结合的多聚核糖体合成，并协同糖基化，穿过高尔基复合体，并积累在蛋白体中，这些蛋白体构成这些细胞中的溶酶体区室。PHA的一些高甘露糖侧链在高尔基复合体中被修饰，并且在成熟的PHA中，它们含有摩尔比为2、3.8、0.6和0.5的N-乙酰葡糖胺、甘露糖、岩藻糖和木糖。这里报道的结果表明，高尔基复合体也是额外的N-乙酰葡糖胺掺入到修饰的侧链的网站。当用[3 H]葡糖胺和分离的高尔基复合体中存在的PHA糖肽标记发育中的子叶时，通过用β-N-乙酰葡糖胺糖苷酶消化糖肽，放射性可作为[3 H]N-乙酰葡糖胺释放，表明残基位于末端位置。PHA到达蛋白体后，缓慢去除这些末端N-乙酰葡糖胺残基，导致修饰侧链的Mr降低。用于动物细胞溶酶体区室的糖蛋白的生物合成中间体含有经N-乙酰葡糖胺覆盖的磷酸基团修饰的高甘露糖侧链，其对温和的酸处理不稳定。当子叶用[32 P]正磷酸盐标记时，从任何亚细胞组分中获得的PHA中没有放射性。当从高尔基复合体中的PHA获得的[3 H]葡糖胺标记的糖肽进行温和的酸水解时，也没有放射性释放。这些结果表明，在植物细胞和动物细胞中，转运到溶酶体区室的蛋白质的分选信号和翻译后加工步骤是不同的。
Cotyledons of the common bean (Phaseolus vulgaris L.) synthesize large amounts of the lectin phytohemagglutinin (PHA) during seed development. The polypeptides of PHA are synthesized by endoplasmic reticulum-bound polysomes and co-translationally glycosylated, pass through the Golgi complex, and accumulate in protein bodies, which constitute the lysosomal compartment in these cells. Some of the high-mannose sidechains of PHA are modified in the Golgi complex, and in mature PHA they contain N-acetylglucosamine, mannose, fucose, and xylose in the molar ratios 2, 3.8, 0.6, and 0.5. The results reported here show that the Golgi complex is also the site of additional N-acetylglucosamine incorporation into the modified sidechains. When developing cotyledons are labeled with [3H]glucosamine and glycopeptides of PHA present in the Golgi complex isolated, the radioactivity can be released as [3H]N- acetylglucosamine by digestion of the glycopeptides with beta-N- acetylglucosaminidase, indicating that the residues are in a terminal position. Arrival of PHA in the protein bodies is followed by the slow removal of these terminal N-acetylglucosamine residues, resulting in a decrease in the Mr of the modified sidechains. The biosynthetic intermediates of the glycoproteins destined for the lysosomal compartments of animal cells contain high-mannose sidechains modified by phosphate groups covered by N-acetylglucosamine that is labile to mild acid treatment. When cotyledons are labeled with [32P]orthophosphate, there is no radioactivity in PHA obtained from any of the subcellular fractions. There is also no release of radioactivity when [3H]glucosamine-labeled glycopeptides obtained from PHA in the Golgi complex are subjected to mild acid hydrolysis. These results indicate that the sorting-signals and posttranslational processing steps for proteins that are transported to the lysosomal compartment are different in plant cells and animal cells.