Plastid Biology
Plastid Biology
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质体生物学
DOI：
10.1007/978-1-4939-1136-3_9
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Jarvis P
中科院分区：
文献类型：
--
作者：
Jarvis P
大多数叶绿体蛋白由核基因组编码为前蛋白。它们进入叶绿体是在翻译后发生的。 N 端前序列（转运肽）包含细胞器靶向信息。它被叶绿体表面的受体成分特异性识别。这些受体是 TOC（叶绿体外膜易位子）复合物的组成部分。与 TIC（叶绿体内包膜易位子）机制一起，它介导蛋白质进入叶绿体。除了受体之外，这些复合物还具有通道、运动和调节功能。许多假定的或实际的组件已被识别。 TOC 受体的多种亚型（可能还有其他一些成分）构成了具有不同客户偏好的单独导入途径的分子基础。这可能会减少高丰度和低丰度前蛋白之间的竞争效应。客户对不同导入途径的偏好也可能促进各种质体类型的分化。除了典型的 TOC/TIC 介导的输入途径外，还确定了蛋白质转运至叶绿体的替代的、机械上不同的途径；其中之一穿过内质网和高尔基体。其他工作揭示了几种通向包膜的蛋白质靶向途径。
Most chloroplast proteins are encoded as preproteins by the nuclear genome. Their import into chloroplasts occurs post-translationally. An N-terminal pre-sequence, the transit peptide, contains the organellar targeting information. It is specifically recognized by receptor components at the chloroplast surface. These receptors are components of the TOC (translocon at theouter envelope membrane ofchloroplasts) complex. Together with the TIC (translocon at theinner envelope membrane ofchloroplasts) machinery, this mediates the import of proteins into chloroplasts. In addition to the receptors, these complexes incorporate channel, motor and regulatory functions. Many putative or actual components have been identified. Multiple isoforms of the TOC receptors (and possibly of some other components) constitute the molecular basis of separate import pathways with distinct client preferences. This perhaps reduces competition effects between highly abundant and less abundant preproteins. Client preferences of different import pathways might also facilitate the differentiation of various plastid types. In addition to the canonical TOC/TIC-mediated import routes, alternative, mechanistically distinct pathways of protein transport to chloroplasts have been identified; one of these passes through the endoplasmic reticulum and Golgi apparatus. Other work has revealed several protein targeting pathways leading to the envelope membranes.