Boutry M, Nagy F, Poulsen C, Aoyagi K, Chua N H
Nature. 1987;328(6128):340-2. doi: 10.1038/328340a0.
Most mitochondrial proteins are encoded by nuclear genes and are synthesized as precursors containing a presequence at the N terminus. In yeast and in mammalian cells, the function of the presequence in mitochondrial targeting has been revealed by chimaeric gene studies. Fusion of a mitochondrial presequence to a foreign protein coding sequence enables the protein to be imported into mitochondria in vitro as well as in vivo. Whether plant mitochondrial presequences function in the same way has been unknown. We have previously isolated and characterized a nuclear gene (atp2-1) from Nicotiana plumbaginifolia that encodes the beta-subunit of the mitochondrial ATP synthase. We have constructed a chimaeric gene comprising a putative atp2-1 presequence fused to the bacterial chloramphenicol acetyltransferase (CAT) coding sequence and introduced it into the tobacco genome. We report here that a segment of 90 amino acids of the N terminus of the beta-subunit precursor is sufficient for the specific targeting of the CAT protein to mitochondria in transgenic plants. Our results demonstrate a high specificity for organelle targeting in plant cells.
大多数线粒体蛋白质由核基因编码，并以前体形式合成，前体在N端含有一个前序列。在酵母和哺乳动物细胞中，通过嵌合基因研究揭示了前序列在线粒体靶向中的功能。将线粒体前序列与外源蛋白质编码序列融合，可使该蛋白质在体外和体内导入线粒体。植物线粒体前序列是否以同样的方式发挥作用尚不清楚。我们之前从烟草中分离并鉴定了一个核基因（atp2-1），它编码线粒体ATP合酶的β亚基。我们构建了一个嵌合基因，该基因包含一个推定的atp2-1前序列与细菌氯霉素乙酰转移酶（CAT）编码序列融合，并将其导入烟草基因组。我们在此报告，β亚基前体N端的一段90个氨基酸足以使CAT蛋白在转基因植物中特异性靶向线粒体。我们的结果证明了植物细胞中细胞器靶向的高度特异性。
