Protein targeting into secondary plastids of chlorarachniophytes
Protein targeting into secondary plastids of chlorarachniophytes
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DOI：
10.1073/pnas.0902578106
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发表时间：
2009-08-04
影响因子：
11.1
通讯作者：
Ishida, Ken-ichiro
中科院分区：
文献类型：
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作者：
Hirakawa, Yoshihisa;Nagamune, Kisaburo;Ishida, Ken-ichiro
大多数质体蛋白质由核基因组编码，因此，需要通过多个被膜转运到质体中。在具有次级质体的多种生物中，核编码的质体前体蛋白（前蛋白）通常具有由内质网（ER）靶向信号肽和转运肽样序列（TPL）组成的N-末端延伸。这种二分靶向肽被认为是将前体蛋白靶向到次级质体中所必需的。在这里，我们新证明了一个藻类组，绿藻的双向靶向肽的功能，并表征的TPL的功能结构域的前体的质体蛋白，ATP合酶δ亚基（AtpD），使用GFP作为报告分子。我们发现，TPL的C-末端部分是重要的，针对AtpD前蛋白从ER到绿藻质体，和几个带正电荷的氨基酸在TPL也是必要的运输前蛋白跨越2最内层质体膜。与其他具有次生质体的类群相比，绿藻类植物的TPL功能域是独特的，这可能是由其质体的独立获得引起的。
Most plastid proteins are encoded by the nuclear genome, and consequently, need to be transported into plastids across multiple envelope membranes. In diverse organisms possessing secondary plastids, nuclear-encoded plastid precursor proteins (preproteins) commonly have an N-terminal extension that consists of an endoplasmic reticulum (ER)-targeting signal peptide and a transit peptide-like sequence (TPL). This bipartite targeting peptide is believed to be necessary for targeting the preproteins into the secondary plastids. Here, we newly demonstrate the function of the bipartite targeting peptides of an algal group, chlorarachniophytes, and characterize the functional domains of the TPL in the precursor of a plastid protein, ATP synthase delta subunit (AtpD), using a GFP as a reporter molecule. We show that the C-terminal portion of the TPL is important for targeting the AtpD preprotein from the ER into the chlorarachniophyte plastids, and several positively charged amino acids in the TPL are also necessary for transporting the preprotein across the 2 innermost plastid membranes. Compared with other groups with secondary plastids, the TPL functional domains of the chlorarachniophytes are unique, which might be caused by independent acquisition of their plastids.