Plastid Development in Leaves during Growth and Senescence
Plastid Development in Leaves during Growth and Senescence
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生长和衰老过程中叶子的质体发育
DOI：
10.1007/978-94-007-5724-0_12
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Ling Q
中科院分区：
文献类型：
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作者：
Ling Q
大部分叶绿体蛋白质组编码在核基因组中，需要在翻译后输入。这些输入蛋白的细胞器靶向信息存在于一个n端先导序列，即转运肽，它与叶绿体表面的受体成分特异性结合。这些受体成分是TOC（叶绿体外包膜转座子）复合物的一部分，它与TIC（叶绿体内包膜转座子）机制一起，介导前体蛋白在叶绿体中的易位。除受体外，这些复合物还具有通道、运动和调节功能。该TOC/TIC仪器的许多组成部分已被确定。TOC受体的多种同种异构体（可能还有一些其他成分）使不同的输入途径具有不同的底物偏好，也许这样一来，不丰富的蛋白质就可以在没有来自光合机构的丰富蛋白质的严重竞争的情况下输入。不同的输入途径也可能在不同质体类型的分化中起作用。虽然许多研究都集中在这些典型的TOC/ tic介导的进口途径上，但许多研究已经揭示了采用不同机制的叶绿体的替代蛋白质运输途径；其中一条通过内质网和高尔基体。最近的其他研究揭示了几种通往包膜本身的蛋白质靶向途径。
Much of the chloroplast proteome is encoded in the nuclear genome and needs to be imported post-translationally. Information for the organellar targeting of these imported proteins lies in an N-terminal leader sequence, the transit peptide, which is specifically bound by receptor components at the chloroplast surface. These receptor components are part of the TOC (translocon at theouter envelope membrane ofchloroplasts) complex, which, together with the TIC (translocon at theinner envelope membrane ofchloroplasts) machinery, mediates the translocation of precursor proteins into chloroplasts. Apart from the receptors, these complexes incorporate channel, motor and regulatory functions. Many components of this TOC/TIC apparatus have been identified. Multiple isoforms of the TOC receptors (and possibly of some other components) enable the operation of different import pathways with different substrate preferences, perhaps so that non-abundant proteins can be imported without serious competition from highly-abundant proteins of the photosynthetic apparatus. The different import pathways might also play a role in the differentiation of different plastid types. While much research has focused on these canonical TOC/TIC-mediated import routes, a number of studies have revealed alternative protein transport pathways to chloroplasts that employ different mechanisms; one of these passes through the endoplasmic reticulum and the Golgi apparatus. Other recent studies have revealed several protein targeting pathways leading to the envelope itself.