Alternative Processing of Arabidopsis Hsp70 Precursors during Protein Import into Chloroplasts
Alternative Processing of Arabidopsis Hsp70 Precursors during Protein Import into Chloroplasts
复制标题
DOI：
10.1271/bbb.80408
复制
发表时间：
2008-11-01
影响因子：
1.6
通讯作者：
Akita, Mitsuru
中科院分区：
文献类型：
--
作者：
Ratnayake, R. M. Udayangani;Inoue, Hitoshi;Akita, Mitsuru
在蛋白质进入叶绿体的过程中，先前报道的豌豆Hsp70蛋白之一（Hsp70- iap）定位于叶绿体膜间空间，被发现与易位前体蛋白相互作用，但Hsp70- iap基因尚未确定。为了鉴定Hsp70- iap的拟南芥同源物，我们采用了体外蛋白导入实验来确定三个拟南芥Hsp70同源物（AtHsp70-6至8）的定位，预测其用于叶绿体靶向。将AtHsp70-6和AtHsp70-7导入叶绿体，加工成大小相近的成熟形态。此外，还观察到较小尺寸的AtHsp70-6加工形式。这两种AtHsp70蛋白的所有加工形式都定位于基质中。无细胞器加工实验表明，AtHsp70-6和AtHsp70-7的大加工形式都是由基质加工肽酶切割的，而AtHsp70-6的小加工形式是由一种未指明的肽酶产生的。
During protein import into chloroplasts, one of the Hsp70 proteins in pea (Hsp70-IAP), previously reported to localize in the intermembrane space of chloroplasts, was found to interact with the translocating precursor protein but the gene for Hsp70-IAP has not been identified yet. In an attempt to identify the Arabidopsis homolog of Hsp70-IAP, we employed an in vitro protein import assay to determine the localization of three Arabidopsis Hsp70 homologs (AtHsp70-6 through 8), predicted for chloroplast targeting. AtHsp70-6 and AtHsp70-7 were imported into chloroplasts and processed into similar-sized mature forms. In addition, a smaller-sized processed form of AtHsp70-6 was observed. All the processed forms of both AtHsp70 proteins were localized in the stroma. Organelle-free processing assays revealed that the larger processed forms of both AtHsp70-6 and AtHsp70-7 were cleaved by stromal processing peptidase, whereas the smaller processed form of AtHsp70-6 was produced by an unspecified peptidase.