VESICLE TRANSPORT AND PROCESSING OF THE PRECURSOR TO 2S-ALBUMIN IN PUMPKIN
VESICLE TRANSPORT AND PROCESSING OF THE PRECURSOR TO 2S-ALBUMIN IN PUMPKIN
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DOI：
10.1046/j.1365-313x.1993.04050793.x
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发表时间：
1993-11-01
期刊：
影响因子：
7.2
通讯作者：
NISHIMURA, M
中科院分区：
文献类型：
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作者：
HARAHISHIMURA, I;TAKEUCHI, Y;NISHIMURA, M
脉冲追踪标记的发育中的南瓜子叶的细胞分级表明，2S白蛋白的前体蛋白从内质网运输到致密的囊泡，然后到液泡，其中pro 2S白蛋白被加工成成熟的2S白蛋白。免疫细胞化学分析表明，南瓜2S白蛋白前体（16578 Da）的一级结构由一个直径约300 nm的致密囊泡介导。在N-末端存在疏水性信号肽表明前体是前蛋白原，其在信号肽裂解后转化为pro 2S白蛋白。分离的囊泡中的pro 2S白蛋白的N-末端测序显示，信号肽在prepro 2S白蛋白的丙氨酸残基22的C-末端侧上共剪切。相比之下，翻译后裂解发生在天冬酰胺残基35和74的C-末端侧，这是保守的前体之间的2S白蛋白从不同的植物。亲水性分析表明，这两个天冬酰胺残基位于亲2S白蛋白的亲水区域。这些研究结果表明，液泡加工酶可以识别暴露的天冬酰胺残基的pro 2S白蛋白的分子表面上，并切割每个天冬酰胺残基的C-末端侧的肽键，以产生成熟的2S白蛋白在液泡。
Cell fractionation of pulse-chase-labeled developing pumpkin cotyledons demonstrated that proprotein precursor to 2S albumin is transported from the endoplasmic reticulum to dense vesicles and then to the vacuoles, in which pro2S albumin is processed to the mature 2S albumin. Immunocytochemical analysis showed that dense vesicles of about 300 nm in diameter mediate the transport of pro2S albumin to the vacuoles.The primary structure of the precursor (1 6 578 Da) to pumpkin 2S albumin has been deduced from the nucleotide sequence of an isolated cDNA insert. The presence of a hydrophobic signal peptide at the N-terminus indicates that the precursor is a preproprotein that is converted into pro2S albumin after cleavage of the signal peptide. N-terminal sequencing of the pro2S albumin in the isolated vesicles revealed that the signal peptide is cleaved off co-translationally on the C-terminal side of alanine residue 22 of prepro2S albumin. By contrast, post-translational cleavages occur on the C-terminal sides of asparagine residues 35 and 74, which are conserved among precursors to 2S albumin from different plants. Hydropathy analysis revealed that the two asparagine residues are located in the hydrophilic regions of pro2S albumin. These findings suggest that a vacuolar processing enzyme can recognize exposed asparagine residues on the molecular surface of pro2S albumin and cleave the peptide bond on the C-terminal side of each asparagine residue to produce mature 2S albumin in the vacuoles.