An essential role for chloroplast heat shock protein 90 (Hsp90C) in protein import into chloroplasts
An essential role for chloroplast heat shock protein 90 (Hsp90C) in protein import into chloroplasts
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DOI：
10.1073/pnas.1219229110
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发表时间：
2013-02-19
影响因子：
11.1
通讯作者：
Schnell, Danny J.
中科院分区：
文献类型：
--
作者：
Inoue, Hitoshi;Li, Ming;Schnell, Danny J.
叶绿体热休克蛋白 90 (Hsp90C) 代表分子伴侣 Hsp90 家族中高度保守的亚家族，其功能尚未确定。我们确定 Hsp90C 是在翻译后导入分离叶绿体期间与核编码前蛋白的导入中间体相互作用的组分。 Hsp90C 与蛋白质输入成分复合物特异性共沉淀，其中包括 Tic110、Tic40、Toc75、Tic22 以及基质伴侣 Hsp93 和 Hsp70。 Radicicol 是 Hsp90 ATPase 活性的抑制剂，可逆地抑制多种前蛋白在跨内膜转位过程中的输入，表明 Hsp90C 在膜转位到细胞器中发挥作用。 Hsp90C 在拟南芥中由单个基因编码，Hsp90C 基因中的插入突变是胚胎致死的，表明分子伴侣在植物活力中的重要功能。基于这些结果，我们提出 Hsp90C 在叶绿体基质中的伴侣复合物中发挥作用，以促进蛋白质输入细胞器期间的膜易位。
Chloroplast heat shock protein 90 (Hsp90C) represents a highly conserved subfamily of the Hsp90 family of molecular chaperones whose function has not been defined. We identified Hsp90C as a component that interacts with import intermediates of nuclear-encoded preproteins during posttranslational import into isolated chloroplasts. Hsp90C was specifically coprecipitated with a complex of protein import components, including Tic110, Tic40, Toc75, Tic22, and the stromal chaperones, Hsp93 and Hsp70. Radicicol, an inhibitor of Hsp90 ATPase activity, reversibly inhibited the import of a variety of preproteins during translocation across the inner envelope membrane, indicating that Hsp90C functions in membrane translocation into the organelle. Hsp90C is encoded by a single gene inArabidopsis thaliana, and insertion mutations in the Hsp90C gene are embryo lethal, indicating an essential function for the chaperone in plant viability. On the basis of these results, we propose that Hsp90C functions within a chaperone complex in the chloroplast stroma to facilitate membrane translocation during protein import into the organelle.