Lesnik Chen, Cohen Yifat, Atir-Lande Avigail, Schuldiner Maya, Arava Yoav
Department of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
Nat Commun. 2014 Dec 9;5:5711. doi: 10.1038/ncomms6711.
It is well established that import of proteins into mitochondria can occur after their complete synthesis by cytosolic ribosomes. Recently, an additional model was revived, proposing that some proteins are imported co-translationally. This model entails association of ribosomes with the mitochondrial outer membrane, shown to be mediated through the ribosome-associated chaperone nascent chain-associated complex (NAC). However, the mitochondrial receptor of this complex is unknown. Here, we identify the Saccharomyces cerevisiae outer membrane protein OM14 as a receptor for NAC. OM14Δ mitochondria have significantly lower amounts of associated NAC and ribosomes, and ribosomes from NAC[Δ] cells have reduced levels of associated OM14. Importantly, mitochondrial import assays reveal a significant decrease in import efficiency into OM14Δ mitochondria, and OM14-dependent import necessitates NAC. Our results identify OM14 as the first mitochondrial receptor for ribosome-associated NAC and reveal its importance for import. These results provide a strong support for an additional, co-translational mode of import into mitochondria.
蛋白质在胞质核糖体完全合成后进入线粒体这一过程已得到充分证实。最近，另一种模型被重新提出，该模型认为一些蛋白质是共翻译导入的。此模型涉及核糖体与线粒体外膜的结合，已表明这是通过核糖体相关伴侣新生链相关复合物（NAC）介导的。然而，该复合物的线粒体受体尚不清楚。在这里，我们确定酿酒酵母外膜蛋白OM14是NAC的受体。OM14Δ线粒体中NAC和核糖体的结合量显著降低，而来自NAC[Δ]细胞的核糖体与OM14的结合水平也降低。重要的是，线粒体导入实验表明导入OM14Δ线粒体的效率显著下降，且依赖于OM14的导入需要NAC。我们的结果确定OM14是核糖体相关NAC的首个线粒体受体，并揭示了其对导入的重要性。这些结果为线粒体导入的另一种共翻译模式提供了有力支持。
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