The correct targeting and insertion of tail-anchored (TA) integral membrane proteins is critical for cellular homeostasis. TA proteins are defined by a hydrophobic transmembrane domain (TMD) at their C-terminus and are targeted to either the ER or mitochondria. Derived from experimental measurements of a few TA proteins, there has been little examination of the TMD features that determine localization. As a result, the localization of many TA proteins are misclassified by the simple heuristic of overall hydrophobicity. Because ER-directed TMDs favor arrangement of hydrophobic residues to one side, we sought to explore the role of geometric hydrophobic properties. By curating TA proteins with experimentally determined localizations and assessing hypotheses for recognition, we bioinformatically and experimentally verify that a hydrophobic face is the most accurate singular metric for separating ER and mitochondria-destined yeast TA proteins. A metric focusing on an 11 residue segment of the TMD performs well when classifying human TA proteins. The most inclusive predictor uses both hydrophobicity and C-terminal charge in tandem. This work provides context for previous observations and opens the door for more detailed mechanistic experiments to determine the molecular factors driving this recognition.

中文翻译：

---

决定真核生物尾锚定膜蛋白分选的基于序列的特征

尾锚定 (TA) 整合膜蛋白的正确靶向和插入对于细胞稳态至关重要。TA 蛋白由其 C 端的疏水跨膜结构域 (TMD) 定义，并靶向 ER 或线粒体。源自对一些 TA 蛋白的实验测量，几乎没有对确定定位的 TMD 特征进行检查。因此，许多 TA 蛋白的定位被整体疏水性的简单启发式错误分类。因为 ER 导向的 TMD 有利于将疏水残基排列到一侧，所以我们试图探索几何疏水特性的作用。通过使用实验确定的定位来管理 TA 蛋白并评估识别假设，我们通过生物信息学和实验验证了疏水面是分离 ER 和线粒体目的地酵母 TA 蛋白的最准确的单一指标。在对人类 TA 蛋白进行分类时，侧重于 TMD 的 11 个残基片段的指标表现良好。最具包容性的预测器同时使用疏水性和 C 末端电荷。这项工作为以前的观察提供了背景，并为更详细的机械实验打开了大门，以确定驱动这种识别的分子因素。