Van Steeg H, Oudshoorn P, Van Hell B, Polman J E, Grivell L A
EMBO J. 1986 Dec 20;5(13):3643-50. doi: 10.1002/j.1460-2075.1986.tb04694.x.
The mitochondrial matrix enzyme manganese superoxide dismutase (SOD) of Saccharomyces cerevisiae is encoded in the nucleus. It is synthesized as a precursor with an NH2-terminal extension of 26 amino acids which is cleaved off during import into the mitochondrion. Fusions between the NH2-terminal 34 amino acids of SOD and the cytosolic proteins invertase of yeast and mouse dihydrofolate reductase (DHFR) were tested for in vitro binding and import into mitochondria. Efficient translocation over the mitochondrial membranes takes place in the case of the SOD-DHFR fusion. The SOD-invertase fusion protein does not get translocated and binds to the organelle with only low efficiency. Yeast transformants harbouring the SOD-invertase fusion gene accumulate approximately 95% of the hybrid protein in the cytosol. The remaining material is found in the interior of the mitochondrion, loosely attached to the inner membrane. We conclude that the pre-sequence of SOD is able to deliver a passenger protein to the mitochondrion. The efficiency of protein delivery and translocation across the membrane is, however, influenced by the passenger protein.
酿酒酵母的线粒体基质酶锰超氧化物歧化酶（SOD）由细胞核编码。它作为一种前体合成，带有26个氨基酸的NH2末端延伸序列，在导入线粒体的过程中被切除。对SOD的NH2末端34个氨基酸与酵母胞质蛋白转化酶和小鼠二氢叶酸还原酶（DHFR）之间的融合体进行了体外结合和导入线粒体的测试。在SOD-DHFR融合体的情况下，线粒体膜上发生了高效的转运。SOD-转化酶融合蛋白没有发生转运，仅以低效率与细胞器结合。携带SOD-转化酶融合基因的酵母转化体在细胞质中积累了约95%的杂合蛋白。其余物质存在于线粒体内，松散地附着在内膜上。我们得出结论，SOD的前序列能够将一个乘客蛋白递送至线粒体。然而，蛋白递送和跨膜转运的效率受乘客蛋白的影响。
