Tarassov I, Entelis N, Martin R P
UPR 9005 du CNRS, Mécanismes Moléculaires de la Division Cellulaire et du Développement, Strasbourg, France.
J Mol Biol. 1995 Jan 27;245(4):315-23. doi: 10.1006/jmbi.1994.0026.
In Saccharomyces cerevisiae, one of the two cytoplasmic lysine-tRNA isoacceptors, tRNA(LysCUU), is the only nuclear-coded tRNA species to be mitochondrially-imported. Using an in vitro assay of tRNA import, we have studied if the mitochondrial protein translocation machinery is also involved in the mitochondrial targeting of this tRNA. As for protein import, tRNA import also requires the integrity of proteins exposed onto the mitochondrial outer membrane and is dependent upon energy and membrane eletrochemical potential. Furthermore, partial ATP-depletion of the import system leads to stabilization of a translocation intermediate containing the tRNA. In this case, the import of the tRNA can be completed after addition of a new source of energy, even without restoration of the membrane electrochemical potential and without further addition of cytoplasmic proteins. Outer and inner mitochondrial membrane receptors shown to participate in translocation of mitochondrial pre-proteins (MOM19 and MPI1/MIM44, respectively) are also important for import of the tRNA, in vitro as well as in vivo. In contrast, the outer membrane receptor MOM72 is dispensable for the import. Taken together, these results demonstrate that a functional mitochondrial protein translocation apparatus is required for the mitochondrial import of the yeast tRNA(LysCUU).
在酿酒酵母中，两种细胞质赖氨酸 - tRNA同工受体之一，即tRNA（LysCUU），是唯一经线粒体导入的核编码tRNA种类。利用tRNA导入的体外测定法，我们研究了线粒体蛋白质转运机制是否也参与这种tRNA的线粒体靶向运输。与蛋白质导入一样，tRNA导入也需要暴露于线粒体外膜的蛋白质的完整性，并且依赖于能量和膜电化学电位。此外，导入系统的部分ATP消耗会导致含有tRNA的转运中间体的稳定。在这种情况下，即使在不恢复膜电化学电位且不进一步添加细胞质蛋白质的情况下，添加新的能量源后tRNA的导入仍可完成。已证明参与线粒体前体蛋白转运的线粒体外膜和内膜受体（分别为MOM19和MPI1 / MIM44）对于tRNA的体外和体内导入也很重要。相比之下，外膜受体MOM72对于导入是可有可无的。综上所述，这些结果表明酵母tRNA（LysCUU）的线粒体导入需要功能性的线粒体蛋白质转运装置。
