Function of a novel SPFH domain protein in bacteria

令人惊讶的是，细菌细胞被划分为功能区域和区域。这种划分包括质膜。包括我的实验室在内的几个实验室的研究表明，像Flotillins这样的支架蛋白有助于将膜组织成功能域。此外，一些细胞过程被认为依赖于这种膜的区隔，确切的分子机制仍然相当难以捉摸。Flotillins共享一个被称为SPFH结构域的签名序列。该蛋白结构域存在于口腔蛋白、禁止蛋白、Flotillins蛋白和细菌HflK/C蛋白中。在所有情况下，SPFH结构域都被证明有助于蛋白质齐聚，这可能是发挥分子支架功能的必要条件。近年来，细菌Flotillins的研究受到了极大的关注，因为Flotillin组装的零突变或化学失活会对细胞产生多效性作用，导致生物膜形成和细胞生长分化的功能受损。Flotillins只与高度有序的膜结合，因此这些SPFH蛋白被认为是所谓的脂筏的标志蛋白。我们最近在枯草芽孢杆菌中发现了SPFH结构域蛋白家族的一个新成员。我们的初步工作表明，该蛋白定位于液体无序的膜区，并参与细胞应激反应。遗传和蛋白质组学分析表明，这种新的SPFH蛋白与一般应激反应途径和细胞被膜应激密切相关。与fltillins不同的是，这种SPFH结构域蛋白不与质膜本身结合，而需要两个在同一操纵子中编码的膜完整蛋白。膜复合体只有在压力条件下才能组装，我们假设这个复合体在细菌对外部细胞包膜压力的感知和反应中发挥着核心作用。

Bacterial cells are surprisingly compartmentalized into functional areas and domains. This compartmentalization includes the plasma membrane. Research from several laboratories, including mine, has shown that scaffold proteins such as flotillins help to organize the membrane into functional domains. Also several cellular processes are thought to rely on this membrane compartmentalization the precise molecular mechanisms are still rather elusive. Flotillins share a signature sequence that has been termed SPFH domain. This protein domain is found in stomatins, prohibitions, flotillins and the bacterial HflK/C proteins. In all cases the SPFH domain has been shown to contribute to protein oligomerization, likely a necessity to function as molecular scaffold. Research on bacterial flotillins has gained a tremendous interest in recent years because null mutations or chemical inactivation of flotillin assembly has pleiotropic effects on cells and leads to impaired functions in biofilm formation and cellular growth and differentiation. Flotillins exclusively associate with highly ordered membranes and hence it was proposed that these SPFH proteins are marker proteins for so-called lipid rafts. We have recently discovered a new member of the SPFH domain family of proteins in Bacillus subtilis. Our preliminary work revealed that this protein localizes to liquid disordered membrane regions and that it is involved in cellular stress response. Genetic and proteomic analyses revealed a tight link of this novel SPFH protein to the general stress response pathway and to cell envelope stress. Unlike flotillins, this SPFH domain protein does not bind to the plasma membrane itself, but requires tow membrane integral proteins that are encoded in the same operon. The membrane complex only assembles under stress conditions and we hypothesize that this complex plays a central role in the perception and response to external cell envelope stress in bacteria.