Magalhães P J, Andreu A L, Schon E A
Department of Neurology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Mol Biol Cell. 1998 Sep;9(9):2375-82. doi: 10.1091/mbc.9.9.2375.
Mammalian mitochondrial ribosomes contain two prokaryotic-like rRNAs, 12S and 16S, both encoded by mitochondrial DNA. As opposed to cytosolic ribosomes, however, these ribosomes are not thought to contain 5S rRNA. For this reason, it has been unclear whether 5S rRNA, which can be detected in mitochondrial preparations, is an authentic organellar species imported from the cytosol or is merely a copurifying cytosol-derived contaminant. We now show that 5S rRNA is tightly associated with highly purified mitochondrial fractions of human and rat cells and that 5S rRNA transcripts derived from a synthetic gene transfected transiently into human cells are both expressed in vivo and present in highly purified mitochondria and mitoplasts. We conclude that 5S rRNA is imported into mammalian mitochondria, but its function there still remains to be clarified.
哺乳动物线粒体核糖体含有两种类似原核生物的rRNA，即12S和16S，二者均由线粒体DNA编码。然而，与胞质核糖体不同的是，这些核糖体被认为不含有5S rRNA。因此，目前尚不清楚在线粒体提取物中检测到的5S rRNA是从胞质溶胶中导入的真正的细胞器成分，还是仅仅是一种共纯化的源自胞质溶胶的污染物。我们现在表明，5S rRNA与人和大鼠细胞的高度纯化线粒体组分紧密相关，并且源自瞬时转染入人细胞的合成基因的5S rRNA转录本在体内均有表达，并存在于高度纯化的线粒体和线粒体膜间隙中。我们得出结论，5S rRNA被导入哺乳动物线粒体，但其在那里的功能仍有待阐明。
