Small membrane proteins as organizers of the bacterial membrane

小膜蛋白被定义为长度小于50个氨基酸的疏水蛋白，主要由单个跨膜结构域组成。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，它们是膜蛋白中最不为人所知的一类。细菌中的小膜蛋白参与了重要的生理过程，如抵抗应激条件或促进膜蛋白复合物的组装。虽然它们在膜蛋白复合物组装过程中作为膜伴侣或衔接蛋白的作用已在少数情况下得到证实，但它们在细胞应激反应中的作用尚未得到详细分析。为了详细了解小膜蛋白的分子功能，必须确定它们在膜内和膜两侧的相互作用伙伴。选定的小膜模型蛋白的相互作用将通过位点定向体内交联结合质谱测定。这将有助于确定小膜蛋白与已知应激反应途径的合作关系，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，特别是这些蛋白是在膜内形成更大的簇还是微结构域。这将通过电子和荧光显微镜分析，以响应内部和外部的压力刺激。此外，小膜蛋白对膜特性的影响，如厚度或流动性，将通过生物物理方法确定。小膜蛋白可作为抗抗菌肽或毒素-抗毒素系统中毒性肽的细胞保护系统。这一假设将通过进行生长实验和分析膜稳定性来验证。总之，为了全面了解小膜生物学，我们的目标是使用多学科方法来鉴定小膜蛋白的相互作用组，揭示其表达对膜稳定性，结构和应激反应的细胞和分子后果，以及它们参与中和毒性肽的可能性。为了进行这些意义深远的分析，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，这将允许深入了解这类迄今为止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.