Department of Microbiology and Molecular Genetics, IMRIC, the Hebrew University Faculty of Medicine, Jerusalem, Israel.
mBio. 2013 Oct 15;4(5):e00443-13. doi: 10.1128/mBio.00443-13.
The bacterial cell poles are emerging as subdomains where many cellular activities take place, but the mechanisms for polar localization are just beginning to unravel. The general phosphotransferase system (PTS) proteins, enzyme I (EI) and HPr, which control preferential use of carbon sources in bacteria, were recently shown to localize near the Escherichia coli cell poles. Here, we show that EI localization does not depend on known polar constituents, such as anionic lipids or the chemotaxis receptors, and on the cell division machinery, nor can it be explained by nucleoid occlusion or localized translation. Detection of the general PTS proteins at the budding sites of endocytotic-like membrane invaginations in spherical cells and their colocalization with the negative curvature sensor protein DivIVA suggest that geometric cues underlie localization of the PTS system. Notably, the kinetics of glucose uptake by spherical and rod-shaped E. coli cells are comparable, implying that negatively curved "pole-like" sites support not only the localization but also the proper functioning of the PTS system in cells with different shapes. Consistent with the curvature-mediated localization model, we observed the EI protein from Bacillus subtilis at strongly curved sites in both B. subtilis and E. coli. Taken together, we propose that changes in cell architecture correlate with dynamic survival strategies that localize central metabolic systems like the PTS to subcellular domains where they remain active, thus maintaining cell viability and metabolic alertness.
Despite their tiny size and the scarcity of membrane-bounded organelles, bacteria are capable of sorting macromolecules to distinct subcellular domains, thus optimizing functionality of vital processes. Understanding the cues that organize bacterial cells should provide novel insights into the complex organization of higher organisms. Previously, we have shown that the general proteins of the phosphotransferase system (PTS) signaling system, which governs utilization of carbon sources in bacteria, localize to the poles of Escherichia coli cells. Here, we show that geometric cues, i.e., strong negative membrane curvature, mediate positioning of the PTS proteins. Furthermore, localization to negatively curved regions seems to support the PTS functionality.
细菌细胞极已成为许多细胞活动发生的亚域，但极性定位的机制才刚刚开始揭示。控制细菌中碳源优先利用的一般磷酸转移酶系统（PTS）蛋白，酶 I（EI）和 HPr，最近被证明定位于大肠杆菌细胞极附近。在这里，我们表明 EI 定位不依赖于已知的极性成分，如阴离子脂质或趋化性受体，也不依赖于细胞分裂机制，也不能用核区遮挡或局部翻译来解释。在球形细胞中内吞样膜内陷的出芽位点检测到一般 PTS 蛋白，并且与负曲率传感器蛋白 DivIVA 共定位，表明几何线索是 PTS 系统定位的基础。值得注意的是，球形和杆状大肠杆菌细胞摄取葡萄糖的动力学是可比的，这意味着负曲率的“极样”位点不仅支持 PTS 系统在不同形状的细胞中的定位，还支持其正常功能。与曲率介导的定位模型一致，我们在枯草芽孢杆菌和大肠杆菌中观察到枯草芽孢杆菌的 EI 蛋白存在于强烈弯曲的部位。综上所述，我们提出细胞结构的变化与动态生存策略相关，这些策略将中央代谢系统（如 PTS）定位到它们保持活性的亚细胞域，从而维持细胞活力和代谢警觉性。
尽管细菌体积微小，膜结合细胞器稀少，但它们能够将大分子分拣到不同的亚细胞区室，从而优化重要过程的功能。了解组织细菌细胞的线索应该为高等生物的复杂组织提供新的见解。以前，我们已经表明，磷酸转移酶系统（PTS）信号系统的一般蛋白，控制细菌中碳源的利用，定位于大肠杆菌细胞的极。在这里，我们表明几何线索，即强负膜曲率，介导 PTS 蛋白的定位。此外，定位到负曲率区域似乎支持 PTS 功能。
