ER-SURF protein import into mitochondria Eukaryotic cells contain membrane-bound organelles, defined by distinct protein compositions. Almost all cellular proteins are synthesized in the cytosol, and thus, organelle-resident proteins must be directed to their appropriate location after synthesis. Working in yeast, Hansen et al. identified a protein-targeting paradigm termed ER-SURF, in which the membrane expanse of the endoplasmic reticulum (ER) serves as a “capture net” for mitochondrial proteins. This process productively redirected mitochondrial precursor proteins for efficient mitochondrial import. Thus, two distinct organelles, once thought to be mutually exclusive protein destinations, can cooperate during protein targeting. Science, this issue p. 1118 The endoplasmic reticulum surface plays a part in the productive targeting of membrane proteins to mitochondria. The majority of organellar proteins are translated on cytosolic ribosomes and must be sorted correctly to function. Targeting routes have been identified for organelles such as peroxisomes and the endoplasmic reticulum (ER). However, little is known about the initial steps of targeting of mitochondrial proteins. In this study, we used a genome-wide screen in yeast and identified factors critical for the intracellular sorting of the mitochondrial inner membrane protein Oxa1. The screen uncovered an unexpected path, termed ER-SURF, for targeting of mitochondrial membrane proteins. This pathway retrieves mitochondrial proteins from the ER surface and reroutes them to mitochondria with the aid of the ER-localized chaperone Djp1. Hence, cells use the expanse of the ER surfaces as a fail-safe to maximize productive mitochondrial protein targeting.

中文翻译：

---

ER 表面修复途径保护酵母中线粒体膜蛋白的输入

ER-SURF 蛋白导入线粒体 真核细胞含有膜结合细胞器，由不同的蛋白质组成定义。几乎所有的细胞蛋白都是在细胞质中合成的，因此，细胞器驻留蛋白在合成后必须被定向到它们的适当位置。Hansen 等人在酵母中工作。确定了一种称为 ER-SURF 的蛋白质靶向范例，其中内质网 (ER) 的膜扩展充当线粒体蛋白质的“捕获网”。这个过程有效地重定向了线粒体前体蛋白，以实现高效的线粒体导入。因此，曾经被认为是相互排斥的蛋白质目的地的两个不同的细胞器可以在蛋白质靶向过程中进行合作。科学，这个问题 p。1118 内质网表面在膜蛋白对线粒体的生产性靶向中起作用。大多数细胞器蛋白质在胞质核糖体上翻译，必须正确分类才能发挥作用。已经确定了过氧化物酶体和内质网 (ER) 等细胞器的靶向途径。然而，关于线粒体蛋白靶向的初始步骤知之甚少。在这项研究中，我们在酵母中使用了全基因组筛选，并确定了对线粒体内膜蛋白 Oxa1 的细胞内分选至关重要的因素。筛选发现了一条意想不到的路径，称为 ER-SURF，用于靶向线粒体膜蛋白。该途径从 ER 表面检索线粒体蛋白，并在 ER 定位的分子伴侣 Djp1 的帮助下将它们重新路由到线粒体。因此，