Roles of molecular interactions in the control of cellular hydration by bacterial osmosensing transporter ProP

蜂窝环境的物理特性随时间和空间而变化。它们包括温度、静水压力和渗透压。改变环境渗透压会导致水流入或流出细胞，从而改变细胞的水合作用，损害细胞的功能。水跟随溶质而来，因此可以通过在包围每个细胞的膜上移动溶质来缓解水通量。这些溶质包括盐、类似氨基酸的化合物和糖。渗透性下激波引起细胞肿胀，并通过张力敏感的膜通道触发溶质释放，以避免细胞破裂。渗透性上激波导致细胞收缩，并通过渗透感应转运蛋白触发溶质吸收，以防止脱水。 我们的目标是了解渗透诱导的细胞脱水如何通过渗透传感转运蛋白在大肠杆菌和其他细菌中触发和调节溶质吸收。事实上，我们的工作提供了典型的渗透调节转运蛋白。道具蛋白嵌入细胞周围的膜中，并暴露在两个膜表面。PROP结合细胞外可获得的溶质，并在细胞内释放它们。道具泵入细胞的速率(道具活性)取决于它所嵌入的膜的组成和细胞内部的盐度。细胞表面的膜成分各不相同，在杆状大肠杆菌细胞的末端(极点)有大量的支撑物。 我们将测试这一假设，即PROP靶向细胞极点和PROP活性都是由盐依赖的自结合和延伸到细胞内部的PROP结构域的膜结合控制的。通过改变其结构(通过基因编辑)，然后检查产生的道具变体的功能和细胞位置，将确定该区域的关键特征。先进的化学技术(例如，核磁共振和红外光谱)和基于超级计算机的模拟将被用来分析自缔合和膜缔合如何影响PROP及其变体的结构。这将使我们能够直观地看到道具的结构如何依赖于它的亚细胞位置和渗透压。 PROP作为研究两个基本现象的范例：渗透传感和蛋白质在细胞内的定位。许多生物过程是由溶质与蛋白质或核酸受体之间的结构特异性(锁和钥匙)相互作用产生的。我们的目标是了解允许细胞检测物理刺激(如渗透压力)的不同原理。通过推断大肠杆菌细胞如何感知和控制自己的物理特性，我们阐明了促进微生物、动物和植物的健康和生存的机制。例如，这种机制对食物和水供应中的细菌、肾脏细胞和盐碱地中的农作物的生存至关重要。

Physical properties of cellular environments vary over time and space. They include the temperature, the hydrostatic pressure and the osmotic pressure. Changing environmental osmotic pressure causes water to flow into or out of cells, thereby changing their hydration and impairing their functions. Water follows solutes, so water fluxes can be mitigated by moving solutes across the membrane that encloses each cell. Those solutes include salts, amino acid-like compounds and sugars. Osmotic downshocks cause cell swelling and trigger solute release via tension-sensitive membrane channels to avoid cell rupture. Osmotic upshocks cause cell shrinkage and trigger solute uptake via osmosensing transporters to forestall dehydration. We aim to understand how osmotically-induced cell dehydration triggers and modulates solute uptake via osmosensing transporter ProP in Escherichia coli and other bacteria. If fact, our work rendered ProP the paradigmatic osmosensing transporter. The ProP protein is embedded in the membrane that surrounds the cell and exposed on both membrane surfaces. ProP binds solutes available outside the cell and releases them inside the cell. The rate at which ProP pumps solutes into cells (ProP activity) depends on the composition of the membrane in which it is embedded and the salinity of the cellular interior. The membrane composition varies over the cell surface, and ProP concentrates at the ends (the poles) of rod-shaped E. coli cells. We will test the hypothesis that both ProP targeting to the cell poles and ProP activity are controlled by salt-dependent self-association and membrane association of a ProP domain that extends into the cellular interior. Key features of that domain will be identified by changing its structure (through gene editing), then examining the function and cellular location of the resulting ProP variants. Advanced chemical techniques (for example, nuclear magnetic resonance and infrared spectroscopies) and supercomputer-based simulations will be used to analyze how self- and membrane-association influence the structures of ProP and its variants. This will allow us to visualize how the structure of ProP depends on its subcellular location and the osmotic pressure. ProP serves as a paradigm for the study of two fundamental phenomena: osmosensing and protein localization within cells. Many biological processes result from structure-specific (lock and key) interactions between solutes and protein or nucleic acid receptors. We aim to understand different principles that allow cells to detect physical stimuli such as osmotic stress. By deducing how E. coli cells sense and control their own physical properties, we elucidate mechanisms that promote the health and survival of microbes, animals and plants. For example, such mechanisms are central to the survival of bacteria in food and water supplies, kidney cells and crop plants in salty soils.