Uncovering the Protein Translocon at the Chloroplast Inner Envelope Membrane
Uncovering the Protein Translocon at the Chloroplast Inner Envelope Membrane
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DOI：
10.1126/science.1229262
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发表时间：
2013-02-01
期刊：
影响因子：
56.9
通讯作者：
Nakai, Masato
中科院分区：
文献类型：
--
作者：
Kikuchi, Shingo;Bedard, Jocelyn;Nakai, Masato
叶绿体需要位于外膜和内膜的蛋白质转座子（分别称为TOC和TIC）来输入数以千计的细胞质合成的前蛋白。然而，TIC转座子的分子特性仍然存在争议。Tic20在内膜形成1兆道尔顿复合物，并直接与易位前蛋白相互作用。我们从拟南芥中纯化了1兆道尔顿复合物，该复合物由Tic20和其他三个重要组分组成，其中一个由叶绿体基因组中神秘的开放阅读框ycf1编码。这四种成分，连同众所周知的TOC成分，被发现与不同的转运前蛋白有化学计量上的关联。当重组成平面脂质双层时，纯化的复合物形成蛋白前敏感通道。因此，这个复合体构成了一个一般的TIC易位。
Chloroplasts require protein translocons at the outer and inner envelope membranes, termed TOC and TIC, respectively, to import thousands of cytoplasmically synthesized preproteins. However, the molecular identity of the TIC translocon remains controversial. Tic20 forms a 1-megadalton complex at the inner membrane and directly interacts with translocating preproteins. We purified the 1-megadalton complex from Arabidopsis, comprising Tic20 and three other essential components, one of which is encoded by the enigmatic open reading frame ycf1 in the chloroplast genome. All four components, together with well-known TOC components, were found stoichiometrically associated with different translocating preproteins. When reconstituted into planar lipid bilayers, the purified complex formed a preprotein-sensitive channel. Thus, this complex constitutes a general TIC translocon.