Bach Juri Niño, Bramkamp Marc
Department of Biology I, Ludwig-Maximilians-University, Munich, Germany.
PLoS One. 2015 Jan 30;10(1):e0116750. doi: 10.1371/journal.pone.0116750. eCollection 2015.
Flotillins are universally conserved proteins that are present in all kingdoms of life. Recently it was demonstrated that the B. subtilis flotillin YuaG (FloT) has a direct influence on membrane domain formation by orchestrating lipid domains. Thereby it allocates a proper environment for diverse cellular machineries. YuaG creates platforms for signal transduction, processes crucial for biofilm formation, sporulation, competence, secretion, and others. Even though, flotillins are an emerging topic of research in the field of microbiology little is known about the molecular architecture of prokaryotic flotillins. All flotillins share common structural elements and are tethered to the membrane N'- terminally, followed by a so called PHB domain and a flotillin domain. We show here that prokaryotic flotillins are, similarly to eukaryotic flotillins, tethered to the membrane via a hairpin loop. Further it is demonstrated by sedimentation assays that B. subtilis flotillins do not bind to the membrane via their PHB domain contrary to eukaryotic flotillins. Size exclusion chromatography experiments, blue native PAGE and cross linking experiments revealed that B. subtilis YuaG can oligomerize into large clusters via the PHB domain. This illustrates an important difference in the setup of prokaryotic flotillins compared to the organization of eukaryotic flotillins.
浮动蛋白是普遍保守的蛋白质，存在于所有生命王国中。最近有研究表明，枯草芽孢杆菌的浮动蛋白YuaG（FloT）通过协调脂质结构域对膜结构域的形成有直接影响。由此，它为各种细胞机制分配了一个合适的环境。YuaG为信号转导创造平台，而信号转导是生物膜形成、孢子形成、感受态、分泌等过程所必需的。尽管如此，浮动蛋白是微生物学领域一个新兴的研究课题，人们对原核生物浮动蛋白的分子结构知之甚少。所有浮动蛋白都有共同的结构元件，在N端与膜相连，随后是一个所谓的PHB结构域和一个浮动蛋白结构域。我们在此表明，原核生物的浮动蛋白与真核生物的浮动蛋白类似，通过一个发夹环与膜相连。此外，沉降实验表明，与真核生物的浮动蛋白相反，枯草芽孢杆菌的浮动蛋白不会通过其PHB结构域与膜结合。尺寸排阻色谱实验、蓝色原胶聚丙烯酰胺凝胶电泳和交联实验表明，枯草芽孢杆菌的YuaG可以通过PHB结构域寡聚成大的簇。这说明了原核生物浮动蛋白的结构与真核生物浮动蛋白的结构相比存在一个重要差异。
