On the impact of precursor unfolding during protein import into chloroplasts.
On the impact of precursor unfolding during protein import into chloroplasts.
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DOI：
10.1093/mp/ssp116
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发表时间：
2010-05
期刊：
影响因子：
27.5
通讯作者：
Maike Ruprecht;T. Bionda;Takehiro K. Sato;Maik S. Sommer;T. Endo;E. Schleiff
中科院分区：
文献类型：
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作者：
Maike Ruprecht;T. Bionda;Takehiro K. Sato;Maik S. Sommer;T. Endo;E. Schleiff
蛋白质跨膜易位是一个基本的细胞过程。细胞器（如线粒体和叶绿体）的大部分蛋白质在细胞质中合成，然后以翻译后的方式输入。前体蛋白至少在易位时必须展开，但也有人假设它们在向细胞器的运输过程中展开。展开是由伴侣和转座子本身控制的。同时，伴侣为导入过程提供能量。通过引入肌蛋白titin的igg样模块与叶绿体靶向氧进化亚基（OE33）的转运肽融合，研究了叶绿体转座子的能量特性。我们的研究结果表明，p(OE33)titin在输入前折叠，并且在叶绿体表面与易位子结合后通过展开启动易位。利用先前通过原子力显微镜分析的一组稳定和不稳定的titin突变体，作为线粒体易位的乘客，我们研究了叶绿体易位提供的展开力。基于这些结果，讨论了一个易位模型。
Protein translocation across membranes is a fundamental cellular process. The majority of the proteins of organelles such as mitochondria and chloroplasts is synthesized in the cytosol and subsequently imported in a post-translational manner. The precursor proteins have to be unfolded at least for translocation, but it has also been assumed that they are unfolded during transport to the organelle in the cytosol. Unfolding is governed by chaperones and the translocon itself. At the same time, chaperones provide the energy for the import process. The energetic properties of the chloroplast translocon were studied by import of the Ig-like module of the muscle protein titin fused to the transit peptide of the chloroplast targeted oxygen evolving complex subunit of 33 kDa (OE33). Our results suggest that p(OE33)titin is folded prior to import and that translocation is initiated by unfolding after having bound to the translocon at the chloroplast surface. Using a set of stabilizing and destabilizing mutants of titin previously analyzed by atomic force microscopy and as passenger for mitochondrial translocation, we studied the unfolding force provided by the chloroplast translocon. Based on these results, a model for translocation is discussed.