The Arabidopsis AtSTE24 is a CAAX protease with broad substrate specificity
The Arabidopsis AtSTE24 is a CAAX protease with broad substrate specificity
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DOI：
10.1074/jbc.m202916200
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发表时间：
2002-08-16
影响因子：
4.8
通讯作者：
Yalovsky, S
中科院分区：
文献类型：
--
作者：
Bracha, K;Lavy, M;Yalovsky, S
在异戊烯化之后，蛋白质在其C-末端进行两个异戊烯基依赖性修饰，这是其亚细胞靶向所需的。首先，去除CAAX盒异戊烯化信号传导基序的三个C-末端残基，随后甲基化异戊烯基半胱氨酸部分的游离羧基。克隆了酵母CAAX蛋白酶STE 24（AFC 1）的拟南芥同源物，并在rce 1 Delta ste 24 Delta突变酵母中表达，以证明功能互补。矮牵牛钙调蛋白CaM 53是终止于CTIL CAAX盒的异戊二烯化蛋白质。偶联的甲基化蛋白水解测定证明了AtSTE 24对CaM 53的加工。此外，AtSTE 24促进GFP-RacU 88402融合蛋白的质膜结合，其终止于CLLM CAAX盒。有趣的是，尽管有大量的序列数据，但在酵母和动物细胞中第二种也是主要的CAAX蛋白酶RCE 1的植物同源物没有被鉴定出来。总之，这些数据表明，AtSTE 24可以处理几个异戊二烯化的蛋白质在植物细胞中，不像它的酵母同系物，它的过程中只有一个交配因子，和它的哺乳动物同系物，异戊二烯基-CAAX底物尚未建立。GFP-AtSTE 24在本氏烟草叶表皮细胞中的瞬时表达表明AtSTE 24仅定位于内质网中，表明植物中的异戊二烯化蛋白在其异戊二烯化后首先靶向内质网。
Following prenylation, the proteins are subject to two prenyl-dependent modifications at their C-terminal end, which are required for their subcellular targeting. First, the three C-terminal residues of the CAAX box prenylation signaling motif are removed, which is followed by methylation of the free carboxyl group of the prenyl cysteine moiety. An Arabidopsis homologue of the yeast CAAX protease STE24 (AFC1) was cloned and expressed in rce1Delta ste24Delta mutant yeast to demonstrate functional complementation. The petunia calmodulin CaM53 is a prenylated protein terminating in a CTIL CAAX box. Coupled methylation proteolysis assays demonstrated the processing of CaM53 by AtSTE24. In addition, AtSTE24 promoted plasma membrane association of the GFP-RacU88402 fusion protein, which terminates with a CLLM CAAX box. Interestingly, a plant homologue of the second and major CAAX protease in yeast and animal cells, RCE1, was not identified despite the availability of vast amounts of sequence data. Taken together, these data suggest that AtSTE24 may process several prenylated proteins in plant cells, unlike its yeast homologue, which processes only a-mating factor, and its mammalian homologue, for which prenyl-CAAX substrates have not been established. Transient expression of GFP-AtSTE24 in leaf epidermal cells of Nicotiana benthamiana showed that AtSTE24 is exclusively localized in the endoplasmic reticulum, suggesting that prenylated proteins in plants are first targeted to the endoplasmic reticulum following their prenylation.