Establishing new techniques to study the cotranslational insertion and folding of membrane proteins

每个细胞都由一个复杂的膜系统组成，其中包含许多不同的膜蛋白。其中一些蛋白质是重要代谢途径的主要成分，如呼吸链和光系统。其他膜蛋白形成通道或跨膜受体，促进细胞与环境之间的信号传递，其功能障碍可能导致囊性纤维化、阿尔茨海默病或癌症等疾病。不幸的是，与水溶性蛋白相比，我们对这些蛋白知之甚少，尽管我们大约四分之一的基因组编码膜蛋白，大约50%的药物靶向膜蛋白。大多数膜蛋白在核糖体合成过程中，通过一个膜通道，即转座子，被整合到膜中。由于对这些早期整合事件基本上一无所知，我的目标是研究原核和真核膜蛋白的膜整合。因此，我的目标是开发基于分子生物学的系统，使我和其他研究人员能够研究这些早期的膜整合事件。细菌的SecM蛋白含有抑制肽，抑制其自身的蛋白质合成。在被阻滞的蛋白链上施加外力可以克服这种抑制作用。因此，阻滞肽可以作为一种力传感器来研究跨膜片段的整合。由于在真核生物中也存在功能相似的阻滞序列，我的另一个目标是开发一个系统，使我能够研究真核生物膜蛋白插入内质网膜。这些结果将有助于更好地理解这些早期折叠事件，并解释为什么跨膜段的氨基酸交换经常导致错误折叠和疾病。

Every cell consists of a complex membrane system that contains many different membrane proteins. Some of these proteins are main components of important metabolic pathways such as the respiratory chain and the photosystems. Other membrane proteins form channels or transmembrane receptors, which facilitate signals between cells and their environment and whose dysfunction can lead to diseases like cystic fibrosis, Alzheimer`s disease or cancer. Unfortunately very little is known about these proteins compared to water-soluble proteins, despite the fact that about one quarter of our genome encodes membrane proteins and about 50 % of all drugs target membrane proteins.Most membrane proteins are integrated into a membrane during their synthesis at a ribosome, through a membrane channel, the translocon. Since essentially nothing is known about these early integration events, I aim to study the membrane integration of pro- and eukaryotic membrane proteins.Therefore, I aim to develop molecular biology based systems that allow me and other researchers to study these early membrane integration events. The bacterial SecM protein contains an arrest peptide, which inhibits its own protein synthesis. An external pulling force on the arrested protein chain can overcome this inhibition. Therefore the arrest peptide can be used as a force sensor to study the integration of transmembrane segments. Since functionally similar arrest-sequences also exist in eukaryotes, I additionally aim to develop a system that allows me to study the insertion of eukaryotic membrane proteins into the membrane of the endoplasmic reticulum. The results will allow a better understanding of these early folding events and could explain why amino acid exchanges in transmembrane segments often lead to misfolding and disease.