Mitochondria are central to energy production, metabolism and signaling, and apoptosis. To make new mitochondria from preexisting mitochondria, the cell needs to import mitochondrial proteins from the cytosol into the mitochondria with the aid of translocators in the mitochondrial membranes. The translocase of the outer membrane (TOM) complex, an outer membrane translocator, functions as an entry gate for most mitochondrial proteins. Although high-resolution structures of the receptor subunits of the TOM complex were deposited in the early 2000s, those of entire TOM complexes became available only in 2019. The structural details of these TOM complexes, consisting of the dimer of the β-barrel import channel Tom40 and four α-helical membrane proteins, revealed the presence of several distinct paths and exits for the translocation of over 1,000 different mitochondrial precursor proteins. High-resolution structures of TOM complexes now open up a new era of studies on the structures, functions, and dynamics of the mitochondrial import system.

中文翻译：

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TOM 复合物在蛋白质导入线粒体中的作用：结构观点

线粒体对于能量产生、代谢和信号传导以及细胞凋亡至关重要。为了从预先存在的线粒体中产生新的线粒体，细胞需要借助线粒体膜中的易位蛋白将线粒体蛋白从胞质溶胶导入线粒体中。外膜转位酶 (TOM) 复合物是一种外膜转位蛋白，充当大多数线粒体蛋白的进入门。尽管 TOM 复合物受体亚基的高分辨率结构在 2000 年代初就已沉积，但整个 TOM 复合物的高分辨率结构直到 2019 年才可用。这些 TOM 复合物的结构细节，由 β-桶输入通道的二聚体组成Tom40 和四种 α-螺旋膜蛋白揭示了 1,000 多种不同线粒体前体蛋白易位的几种不同路径和出口的存在。 TOM 复合物的高分辨率结构现在开启了线粒体输入系统的结构、功能和动力学研究的新时代。