Gupta Arushi, Becker Thomas
Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany.
Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Universität Bonn, Nussallee 11, 53115 Bonn, Germany.
Biochim Biophys Acta Bioenerg. 2021 Jan 1;1862(1):148323. doi: 10.1016/j.bbabio.2020.148323. Epub 2020 Oct 7.
Outer membrane proteins integrate mitochondria into the cellular environment. They warrant exchange of small molecules like metabolites and ions, transport proteins into mitochondria, form contact sites to other cellular organelles for lipid exchange, constitute a signaling platform for apoptosis and inflammation and mediate organelle fusion and fission. The outer membrane contains two types of integral membrane proteins. Proteins with a transmembrane β-barrel structure and proteins with a single or multiple α-helical membrane spans. All outer membrane proteins are produced on cytosolic ribosomes and imported into the target organelle. Precursors of β-barrel and α-helical proteins are transported into the outer membrane via distinct import routes. The translocase of the outer membrane (TOM complex) transports β-barrel precursors across the outer membrane and the sorting and assembly machinery (SAM complex) inserts them into the target membrane. The mitochondrial import (MIM) complex constitutes the major integration site for α-helical embedded proteins. The import of some MIM-substrates involves TOM receptors, while others are imported in a TOM-independent manner. Remarkably, TOM, SAM and MIM complexes dynamically interact to import a large set of different proteins and to coordinate their assembly into protein complexes. Thus, protein import into the mitochondrial outer membrane involves a dynamic platform of protein translocases.
外膜蛋白将线粒体整合到细胞环境中。它们保证了代谢物和离子等小分子的交换，将蛋白质转运到线粒体中，形成与其他细胞器的接触位点以进行脂质交换，构成细胞凋亡和炎症的信号平台，并介导细胞器的融合和分裂。外膜包含两种类型的整合膜蛋白。具有跨膜β-桶结构的蛋白和具有单个或多个α-螺旋跨膜结构域的蛋白。所有外膜蛋白均在胞质核糖体上产生并导入目标细胞器。β-桶蛋白和α-螺旋蛋白的前体通过不同的导入途径转运到外膜中。外膜转位酶（TOM复合体）将β-桶前体转运穿过外膜，分选与组装机器（SAM复合体）将它们插入目标膜中。线粒体导入（MIM）复合体构成α-螺旋嵌入蛋白的主要整合位点。一些MIM底物的导入涉及TOM受体，而其他底物则以不依赖TOM的方式导入。值得注意的是，TOM、SAM和MIM复合体动态相互作用，以导入大量不同的蛋白质并协调它们组装成蛋白质复合体。因此，蛋白质导入线粒体外膜涉及一个动态的蛋白质转位酶平台。
