Integration of tail-anchored proteins into the mitochondrial outer membrane does not require any known import components
Integration of tail-anchored proteins into the mitochondrial outer membrane does not require any known import components
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DOI：
10.1242/jcs.024034
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发表时间：
2008-06-15
影响因子：
4
通讯作者：
Rapaport, Doron
中科院分区：
文献类型：
--
作者：
Kemper, Christian;Habib, Shukry J.;Rapaport, Doron
尾锚定蛋白形成在暴露于胞质溶胶的所有细胞内膜中发现的独特类别的膜蛋白。这些蛋白质在其C-末端具有单一的膜插入序列，并向胞质溶胶显示大的N-末端部分。尽管它们对各种细胞过程很重要，但这些蛋白质被识别并插入其相应靶膜的机制在很大程度上仍不清楚。在这里，我们解决这个问题，并调查尾锚定蛋白居住在线粒体外膜的生物起源。为此，我们开发了一种高度特异性的检测方法来监测模型尾锚定蛋白Fis 1的膜插入。使用这种方法，我们表明，在酵母线粒体中的所有其他进口途径相比，没有进口组件在外膜参与插入过程中的Fis 1。稳态水平的Fis 1和其在体外插入到分离的线粒体不受影响时，线粒体突变在已知的进口因素进行了分析。Fis 1被插入到脂质囊泡中，重要的是，这些囊泡中麦角固醇含量的升高抑制了这种插入。总的来说，这些结果表明，Fis 1被插入到线粒体中的一个新的途径，其中独特的脂质组成的线粒体外膜有助于选择性的过程。因此，这项工作证明了脂质在线粒体蛋白质生物合成中的新作用。
Tail-anchored proteins form a distinct class of membrane proteins that are found in all intracellular membranes exposed to the cytosol. These proteins have a single membrane insertion sequence at their C-terminus and display a large N-terminal portion to the cytosol. Despite their importance for various cellular processes, the mechanisms by which these proteins are recognized at and inserted into their corresponding target membrane remained largely unclear. Here we address this issue and investigate the biogenesis of tail-anchored proteins residing in the mitochondrial outer membrane. To that goal we developed a highly specific assay to monitor the membrane insertion of the model tail-anchored protein Fis1. Using this assay, we show that in contrast to all other import pathways in yeast mitochondria, none of the import components at the outer membrane is involved in the insertion process of Fis1. Both the steady-state levels of Fis1 and its in vitro insertion into isolated mitochondria were unaffected when mitochondria mutated in known import factors were analyzed. Fis1 was inserted into lipid vesicles, and importantly, elevated ergosterol contents in these vesicles inhibited this insertion. Collectively, these results suggest that Fis1 is inserted into mitochondria in a novel pathway where the unique lipid composition of the mitochondrial outer membrane contributes to the selectivity of the process. Thus, this work demonstrates a novel role for lipids in the biogenesis of mitochondrial protein.