Chloroplast Import Signals: The Length Requirement for Translocation In Vitro and In Vivo
Chloroplast Import Signals: The Length Requirement for Translocation In Vitro and In Vivo
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DOI：
10.1016/j.jmb.2010.07.052
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发表时间：
2010-09-24
影响因子：
5.6
通讯作者：
Schleiff, Enrico
中科院分区：
文献类型：
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作者：
Bionda, Tihana;Tillmann, Bodo;Schleiff, Enrico
胞质合成的蛋白质的蛋白质易位需要用于将前体蛋白质靶向到相应隔室的表面以及它们穿过其膜的转移的信号。与过氧化物酶体和内质网易位的信号相反，线粒体和叶绿体转运的信号在长度和氨基酸需求方面不太明确。为了研究在体外和体内的叶绿体易位所需的信号的性质，我们使用的融合蛋白组成的转运肽和Ig样模块的肌肉蛋白肌联蛋白作为乘客。我们观察到，约60个氨基酸的长度比许多实验证实的叶绿体蛋白质的转运肽的长度需要有效的易位。然而，在天然叶绿体前体蛋白的转运肽短于60个氨基酸，延伸似乎是存在的，因为它们被有效地导入细胞器。此外，60个或更多个氨基酸的未折叠多肽段与叶绿体表面的受体的相互作用导致蛋白质易位到叶绿体中的单向性，即使在存在竞争性C-末端过氧化物酶体靶向信号的情况下。这些发现证明了现有的想法，即初始靶向是由N-末端信号定义的，C-末端信号仅在随后被感知。(c)2010爱思唯尔有限公司版权所有。
Protein translocation of cytosolically synthesized proteins requires signals for both targeting of precursor proteins to the surface of the respective compartment and their transfer across its membrane. In contrast to signals for peroxisomal and endoplasmic reticulum translocation, the signals for mitochondrial and chloroplast transport are less well defined with respect to length and amino acid requirements. To study the properties of signals required for translocation into chloroplasts in vitro and in vivo, we used fusion proteins composed of transit peptides and the Ig-like module of the muscle protein titin as passenger. We observed that about 60 amino acids longer than the transit peptide length of many experimentally confirmed chloroplast proteins are required for efficient translocation. However, within native chloroplast precursor proteins with transit peptides shorter than 60 amino acids, extension appears to be present as they are efficiently imported into organelles. In addition, the interaction of an unfolded polypeptide stretch of 60 or more amino acids with receptors at the chloroplast surface results in the unidirectionality of protein translocation into chloroplasts even in the presence of a competing C-terminal peroxisomal targeting signal. These findings prove the existing ideas that initial targeting is defined by the N-terminal signal and that the C-terminal signal is sensed only subsequently. (c) 2010 Elsevier Ltd. All rights reserved.