C-terminal KDEL sequence of a KDEL-tailed cysteine proteinase (sulfhydryl-endopeptidase) is involved in formation of KDEL vesicle and in efficient vacuolar transport of sulfhydryl-endopeptidase
C-terminal KDEL sequence of a KDEL-tailed cysteine proteinase (sulfhydryl-endopeptidase) is involved in formation of KDEL vesicle and in efficient vacuolar transport of sulfhydryl-endopeptidase
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DOI：
10.1104/pp.103.021147
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发表时间：
2003-08-01
期刊：
影响因子：
7.4
通讯作者：
Minamikawa, T
中科院分区：
文献类型：
--
作者：
Okamoto, T;Shimada, T;Minamikawa, T
巯基内肽酶（SH-EP）是一种木瓜蛋白酶型液泡蛋白酶，表达于萌发的芒果种子子叶中，其c端前肽含有可溶蛋白的内质网保留信号KDEL尾。SH-EP通过与高尔基复合物无关的KDEL囊泡（KV）转运到液泡。为了了解SH-EP的KDEL序列的功能，我们在拟南芥和培养的烟草亮黄2细胞中异种表达了野生型SH-EP及其KDEL缺失突变体（SH-EPDeltaKDEL），并分析了它们的细胞内转运途径和定位。结合对转化的拟南芥和烟草细胞的分析结果表明，野生型SH-EP通过KDEL序列被装入kv样囊泡中，并被转运到转化体细胞的液泡中。而在SH-EPDeltaKDEL表达的细胞中，KV不形成/诱导，突变蛋白以分泌为主。因此，KDEL尾部半胱氨酸蛋白酶的c端KDEL序列被认为参与了KV的形成，并参与了蛋白质通过KV的有效空泡运输。
Sulfhydryl-endopeptidase (SH-EP) is a papain-type vacuolar proteinase expressed in cotyledons of germinated Vigna mungo seeds and the enzyme possesses a C-terminal propeptide containing KDEL tail, an endoplasmic reticulum retention signal for soluble proteins. SH-EP is transported to vacuoles via a KDEL vesicle (KV) through a Golgi complex-independent route. To see the function of the KDEL sequence of SH-EP, wild-type SH-EP and its KDEL deletion mutant (SH-EPDeltaKDEL) were heterologously expressed in Arabidopsis and in cultured tobacco Bright Yellow 2 cells, and their intracellular transport pathways and localizations were analyzed. A combination of the results from analyses for transformed Arabidopsis and tobacco (Nicotiana tabacum) cells indicated that wild-type SH-EP is packed into KV-like vesicles through the KDEL sequence and is transported to vacuoles in the cells of transformants. In contrast, KV was not formed/induced in the cells expressing SH-EPDeltaKDEL, and the mutant protein was mainly secreted. Therefore, the C-terminal KDEL sequence of the KDEL-tailed cysteine proteinase is thought to be involved in the formation of KV, and in the efficient vacuolar transport of the proteins through KV.