Tzschoppe K, Kohlwein S D, Rödel G
Institut für Genetik, Technische Universität Dresden, Germany.
Biol Chem. 2000 Dec;381(12):1175-83. doi: 10.1515/BC.2000.145.
The yeast translational activator protein Cbs2p is imported into mitochondria without obvious proteolytic processing. To test the importance of amino-terminal amino acids for mitochondrial targeting we fused varying portions of the N-terminus with green fluorescent protein and examined the intracellular distribution of the reporter protein. We show that the 25 N-terminal amino acids are sufficient to direct the majority of the fusion protein into mitochondria. Cbs2p derivatives lacking 9 to 35 amino acids from the N-terminus fail to complement the respiratory deficiency of a deltacbs2 strain, but are still imported into mitochondria. Therefore Cbs2p contains at least one independent mitochondrial targeting information in addition to the N-terminal signal. We further analyzed the effect of over-expression of Cbs2p on mitochondrial function. Elevated concentrations of Cbs2p lead to slightly impaired mitochondrial gene expression, probably as the result of the formation of inactive Cbs2p aggregates.
酵母翻译激活蛋白Cbs2p可导入线粒体，且无明显的蛋白水解加工过程。为了测试氨基末端氨基酸对于线粒体靶向的重要性，我们将氨基末端的不同部分与绿色荧光蛋白融合，并检测了报告蛋白在细胞内的分布。我们发现，25个氨基末端氨基酸足以将大部分融合蛋白导向线粒体。缺少氨基末端9至35个氨基酸的Cbs2p衍生物无法弥补δcbs2菌株的呼吸缺陷，但仍可导入线粒体。因此，除了氨基末端信号外，Cbs2p至少还包含一个独立的线粒体靶向信息。我们进一步分析了Cbs2p过表达对线粒体功能的影响。Cbs2p浓度升高会导致线粒体基因表达略有受损，这可能是由于形成了无活性的Cbs2p聚集体所致。
