膜蛋白的表达:在无细胞体系中实现功能性表达、折叠和组装

Membrane Protein Expression: Functional Expression,Folding and Assembly Within Cell Free System

膜蛋白在人类和其他物种的生命活动中都起着至关重要的作用.在已完成测序的基因组中,膜蛋白占据30%.药物作用靶向位点、细胞之间的信号传递以及对外界环境的探测等功能,大多是通过生物膜上的特殊膜受体蛋白实现的.膜蛋白研究在工业、环境、国防、医学等领域具有重大意义.嗅觉受体蛋白是一类典型的膜蛋白,属于G蛋白偶联受体家族.嗅觉受体蛋白调控着生物的食物寻找、危险趋避和求偶行为.其主要分布于脊椎动物鼻腔和昆虫触角.嗅觉受体蛋白可以直接识别气味分子,将生物信号转化为电信号,最终传递至神经中枢,进而做出相关应答.膜蛋白的获取并不容易.天然组织中的膜蛋白含量太低不足以支撑学术研究.异源表达难以实现膜蛋白整合上膜,这给膜蛋白的结构和功能研究带来很大挑战.无细胞蛋白质合成系统是一个开放体系,且不依赖细胞活性,是体外表达蛋白质的有效方法.通过无细胞蛋白合成体系,在体外实现膜蛋白二聚体的自组装,将为膜蛋白研究带来全新突破.本文总结了用于无细胞表达的膜蛋白研究进展.

Membrane proteins（MPs） play a crucial role in the life activities of humans and other species, which account for about 30% in all sequenced genomes. Drug targeting sites, cell-to-cell signaling, and detection of the environment mainly depends on specific membrane receptor proteins. MPs have significant theoretical and practical value in industrial, environmental, national defense and other research areas. Olfactory receptor（OR）protein is one kind of typical MPs, belonging to G protein-coupled receptor（GPCR） family. ORs regulate the organism to hunt for food, escape from risks and search for spouses. ORs are mainly distributed in the vertebrate nasal cavity or insect antennae. A series of reactions will be stimulated when the odorants bind with osmoceptors.The stimulus signal will be converted into an electrical signal. Eventually pass to the nervous system and to make the appropriate instructions. It is tough to extract MPs directly from tissues. Heterologous expression of MPs makes it difficult to integrate proteins into membranes, which brings great challenges to the study of structure and function. Cell-free protein synthesis system（CFPS） is an efficient strategy to express proteins in vitro on account of the open system and independence of cell lives. CFPS puts forward new ideas for synthesis and assemblage of MPs. It will be a major breakthrough for the study of structures and functions of MPs when the self-assembly and dimer formation can be accomplished in vitro. Here, we summarize latest progress in using CFPS to express ORs and other MPs.