Small membrane proteins as organizers of the bacterial membrane

小分子膜蛋白是指长度小于50个氨基酸的疏水性蛋白，主要由一个跨膜结构域组成。由于分析方法的改进，在欧盟和原核生物中发现了越来越多的这些蛋白质。然而，它们的功能在大多数情况下是未知的，它们构成了膜蛋白中特征最少的一组。细菌中的小膜蛋白似乎参与了重要的生理过程，如对抗应激条件或促进膜蛋白复合体的组装。虽然它们作为膜伴侣或连接蛋白在膜蛋白复合体组装过程中的作用在少数情况下已有文献记载，但缺乏对它们在细胞应激反应中的作用的详细分析。为了详细了解小分子膜蛋白的分子功能，必须确定它们在膜上和膜两侧的相互作用伙伴。选定的小分子膜模型蛋白的相互作用组将通过体内定点交联结合质谱学来确定。这将有助于确定小膜蛋白与已知应激反应途径的合作，并确定小膜蛋白如何影响这些途径，或者它们本身是否受到应激反应途径的影响。小膜蛋白在细菌细胞中的确切定位在很大程度上是未知的，尤其是这些蛋白是在膜内形成更大的簇还是微域。这将通过电子显微镜和荧光显微镜进行分析，以响应内部和外部的应力刺激。此外，小膜蛋白对膜性质的影响，如膜的厚度或流动性，将通过生物物理方法来确定。小膜蛋白可能作为细胞保护系统来抵御抗菌肽或毒素-抗毒素系统中的有毒多肽。这一假设将通过进行生长实验和分析膜的稳定性来验证。综上所述，为了对小膜生物学有一个全面的了解，我们的目标是用多学科的方法来鉴定小膜蛋白的相互作用组，以揭示它们表达对膜稳定性、结构和应激反应的细胞和分子后果，以及它们参与中和有毒多肽的可能性。对于这些影响深远的分析，我们将与SPP2002的成员合作，采用各种高度相关和复杂的实验策略，这将使我们能够深入了解这类迄今定义不清的膜蛋白的生理相关性。

Small membrane proteins are defined as hydrophobic proteins of less than 50 amino acids in length, which consist primarily of a single transmembrane domain. Due to improved analytical methods, an increasing number of these proteins have been identified in eu- and prokaryotes. However, their function is in most cases unknown and they constitute the least characterized group of membrane proteins. It appears that small membrane proteins in bacteria are involved in important physiological process, like counteracting stress conditions or facilitating the assembly of membrane protein complexes. While their role as membrane chaperone or adaptor protein during the assembly of membrane protein complexes has been document in a few cases, detailed analyses on their role in the cellular stress response are missing. For obtaining a detailed view on the molecular function of small membrane proteins, the identification of their interaction partner in the membrane and on both sides of the membrane is mandatory. The interactome of selected small membrane model proteins will be determined by site-directed in vivo cross-linking in combination with mass spectrometry. This will allow to identify the cooperation of small membrane proteins with known stress response pathway and to determine how small membrane proteins influence these pathways or whether they themselves are influenced by stress response pathways.The exact localization of small membrane proteins in the bacterial cell is largely unknown and it is in particular unknown, whether these proteins form larger cluster or microdomains within the membrane. This will be analysed by electron and fluorescence microscopy, in response to internal and external stress stimuli. In addition, the impact of small membrane proteins on membrane properties, like thickness or fluidity will be determined by biophysical methods.Small membrane proteins might act as cellular protection systems against antimicrobial peptides or against toxic peptides of the toxin-antitoxin systems. This hypothesis will be validated by performing growth experiments and by analysing membrane stability. In summary, for obtaining a comprehensive insight into small membrane biology, we aim to use a multidisciplinary approach for identifying the interactome of small membrane proteins, to reveal the cellular and molecular consequences of their expression on membrane stability, architecture and stress response as well as the possibility that they are involved in neutralizing toxic peptides. For these far-reaching analyses we will employ in cooperation with the members of the SPP2002 a variety of highly relevant and sophisticated experimental strategies, which will allow an in-depth view into the physiological relevance of this so far ill-defined class of membrane proteins.