The preprotein conducting channel at the inner envelope membrane of plastids
The preprotein conducting channel at the inner envelope membrane of plastids
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DOI：
10.1093/emboj/21.11.2616
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发表时间：
2002-06-03
期刊：
影响因子：
11.4
通讯作者：
Soll, J
中科院分区：
文献类型：
--
作者：
Heins, L;Mehrle, A;Soll, J
到目前为止，在叶绿体内被膜上的前蛋白易位涉及五种蛋白：Tic 110，Tic 55，Tic 40，Tic 22和Tic 20。这些蛋白质的分子功能尚未确定。在这里，我们表明，Tic 110构成了前蛋白易位孔的中心部分。依赖于完整的Tic 110的存在下，放射性标记的前蛋白特异性地与分离的内囊泡以及与纯化的重组Tic 110重组到脂质体中相互作用。圆二色谱分析表明，Tic 110主要由β-片层组成，这是一种通常在孔蛋白中发现的结构。在平面脂质双层中，重组Tic 110形成阳离子选择性高电导通道，计算的内孔开口为1.7 nm。纯化的转运肽引起强烈的闪烁和通道的电压依赖性阻断。此外，在内被膜处，描述了肽敏感通道，其显示出与由重组Tic 110形成的通道基本相同的性质。我们的结论是，Tic 110有一个独特的前蛋白结合位点，并作为一个前蛋白易位孔在内包膜膜的功能。
The preprotein translocation at the inner envelope membrane of chloroplasts so far involves five proteins: Tic110, Tic55, Tic40, Tic22 and Tic20. The molecular function of these proteins has not yet been established. Here, we demonstrate that Tic110 constitutes a central part of the preprotein translocation pore. Dependent on the presence of intact Tic110, radiolabelled preprotein specifically interacts with isolated inner envelope vesicles as well as with purified, recombinant Tic110 reconstituted into liposomes. Circular dichroism analysis reveals that Tic110 consists mainly of beta-sheets, a structure typically found in pore proteins. In planar lipid bilayers, recombinant Tic110 forms a cation-selective high-conductance channel with a calculated inner pore opening of 1.7 nm. Purified transit peptide causes strong flickering and a voltage-dependent block of the channel. Moreover, at the inner envelope membrane, a peptide-sensitive channel is described that shows properties basically identical to the channel formed by recombinant Tic110. We conclude that Tic110 has a distinct preprotein binding site and functions as a preprotein translocation pore at the inner envelope membrane.