Ott Martin, Prestele Martin, Bauerschmitt Heike, Funes Soledad, Bonnefoy Nathalie, Herrmann Johannes M
Institut für Physiologische Chemie, Universität München, München, Germany.
EMBO J. 2006 Apr 19;25(8):1603-10. doi: 10.1038/sj.emboj.7601070. Epub 2006 Apr 6.
The genome of mitochondria encodes a small number of very hydrophobic polypeptides that are inserted into the inner membrane in a cotranslational reaction. The molecular process by which mitochondrial ribosomes are recruited to the membrane is poorly understood. Here, we show that the inner membrane protein Mba1 binds to the large subunit of mitochondrial ribosomes. It thereby cooperates with the C-terminal ribosome-binding domain of Oxa1, which is a central component of the insertion machinery of the inner membrane. In the absence of both Mba1 and the C-terminus of Oxa1, mitochondrial translation products fail to be properly inserted into the inner membrane and serve as substrates of the matrix chaperone Hsp70. We propose that Mba1 functions as a ribosome receptor that cooperates with Oxa1 in the positioning of the ribosome exit site to the insertion machinery of the inner membrane.
线粒体基因组编码少数非常疏水的多肽，这些多肽在共翻译反应中插入内膜。线粒体核糖体被招募到膜上的分子过程目前还知之甚少。在这里，我们表明内膜蛋白Mba1与线粒体核糖体的大亚基结合。因此，它与Oxa1的C端核糖体结合结构域协同作用，Oxa1是内膜插入机制的核心成分。在缺乏Mba1和Oxa1的C端时，线粒体翻译产物无法正确插入内膜，并成为基质伴侣蛋白Hsp70的底物。我们提出，Mba1作为一种核糖体受体，与Oxa1协同作用，将核糖体出口位点定位到内膜的插入机制上。
