Molecular evolution of the eukaryotic membrane-trafficking system

膜运输系统是真核生物（人类、植物、酵母等）的一个关键特征，也是在细胞水平上将我们与细菌区分开来的决定性特征之一。它负责我们细胞中大部分物质的正确运动和最终定位。它不仅是人类大脑活动和激素分泌的基础，也是植物健康生长的基础，也是对我们的经济和环境至关重要的各种单细胞生物的正常细胞活动的基础。我们对这个细胞系统如何工作的理解来自于一个小样本的实验生物：我们对它如何进化的理解才刚刚开始探索。尽管如此，有证据表明，膜运输系统在真核生物进化的早期就出现了，其中涉及的主要蛋白质家族可能在10亿多年前就已经出现在我们的祖先身上了。对单个蛋白质家族的详细研究，特别是在该途径的内吞（摄取）臂中，揭示了这种细胞机制如何进化的特定事件和机制的信息。

The membrane-trafficking system is a key characteristic of eukaryotes (humans, plants, yeast, etc.) and one of the defining features that separates us from bacteria at a cellular level. It is responsible for the proper movement and final location of most of the material in our cells. It underlies not only brain activity, and hormone secretion in humans, but healthy plant growth, as well as normal cellular activity in a diverse array of single-celled organisms important for our economy and environment. Our understanding of how this cellular system works is derived from a small sample of experimental organisms: our understanding of how it evolved is only beginning to be explored. Nonetheless, evidence suggests that the membrane-trafficking system arose early-on in eukaryotic evolution, with the major protein families involved likely already having been present in our ancestors over one billion years ago. Detailed studies of individual protein families, particularly in the endocytic (uptake) arm of the pathway, are revealing information about specific events and mechanisms of how this cellular machinery evolved.