A scaffolding protein is a multivalent hub for organizing bacterial cytoplasm

尽管细菌是地球上最简单的生物体，但它却具有生命的普遍特征：它们的组织结构非常精巧。令人惊讶的是，细菌细胞中成千上万种不同蛋白质的混合物是一个自组织系统。这是通过生产分子支架来实现的，分子支架是一种大型的三维多孔网络，它附着在特定的靶蛋白上，并将它们组合成合作网络。将这些支架放置在细胞内确定的位置提供了细菌解剖学的基本形式。虽然细菌支架对细胞生理学有重大影响，但对其结构和功能知之甚少，本项目的主要目标是在分子水平上了解支架及其与靶蛋白的相互作用。第二个目标是了解支架网络在细胞解剖学上表现出巨大差异的相关物种之间是如何不同的。这将为支架网络的可塑性如何促进新细菌物种的进化提供新的见解。细胞内精致组织的概念直接关系到该项目的更广泛影响，这将来自于一个视觉上令人惊叹的交互式显微镜展览的建设，该展览将在怀俄明州的夏延儿童博物馆被数千名儿童观看。 许多细菌通过组装多聚蛋白质支架来组织，这些支架将调节蛋白质组招募到合作网络中。虽然这些支架对细菌生理学和细胞组织有重大影响，但对其结构和功能知之甚少。该项目解决了这一重大的知识差距，具体目标如下：（一）确定一个支架蛋白，称为PopZ，在物种Caulobacter crescentus的直接结合伙伴，并在分子水平上的结合界面的特点。 这将是第一次对细菌支架界面进行全面研究，突变分析将提供精确的细节。(ii)了解PopZ支架的三维结构如何影响网络组装以及PopZ结合蛋白在其中移动的动力学特性。这将是第一项将支架的三维几何形状与其在细胞内的功能联系起来的研究，并且将包括基于经验确定的生物物理参数的颗粒运动的新型数学模型。(iii)将PopZ氨基酸序列的变化与新物种进化过程中细胞组织的变化联系起来。这将是第一项比较亚细胞组织差异较大的物种之间PopZ网络的研究，并将测试支架网络提供相对混杂的结合表面以促进进化变化的假设。该项目还强调了超越基础科学的更广泛的影响。在夏延儿童博物馆创建一个独特的互动活细胞显微镜展览时，研究人员将通过给后代科学家留下深刻印象来激励他们了解亚细胞组织的内在美。

Despite being the simplest organisms on our planet, bacteria exemplify a universal feature of life: they are exquisitely organized. Amazingly, the mixture of many thousands of different proteins in a bacterial cell is a self-organizing system. This is accomplished by the production of molecular scaffolds, which are large, three-dimensional, porous networks that attach to specific target proteins and group them into cooperative networks. The placement of these scaffolds at defined locations within the cell provides a basic form of bacterial anatomy. Although bacterial scaffolds have major influences on cell physiology, relatively little is known about their structure and function, and a major goal of this project is to understand scaffolds and their interactions with target proteins at a molecular level. A second goal is to understand how scaffold networks are different among related species that exhibit large variations in cell anatomy. This will provide novel insight on how the plasticity of scaffold networks facilitates the evolution of new bacterial species. The concept of exquisite organization within cells relates directly to the broader impacts of the project, which will come from the construction of a visually stunning interactive microscope exhibit that will be viewed by thousands of young children at the Children's Museum of Cheyenne, Wyoming. Many bacteria become organized by assembling polymeric protein scaffolds that recruit groups of regulatory proteins into cooperative networks. Although these scaffolds have major influences on bacterial physiology and cell organization, relatively little is known about their structure and function. This project addresses this significant knowledge gap with the following specific aims: (i) Identify the direct binding partners of a scaffolding protein, called PopZ, in the species Caulobacter crescentus, and characterize the binding interfaces at a molecular level. This will be the first comprehensive study of a bacterial scaffold interface, with mutational analyses that will provide a precise level of detail. (ii) Understand how the three-dimensional structure of the PopZ scaffold influences network assembly and the kinetic properties of the PopZ-binding proteins moving within it. This will be the first study to relate the three-dimensional geometry of the scaffold to its function within the cell, and will include novel mathematical models of particle movements based on empirically determined biophysical parameters. (iii) Connect changes in the PopZ amino acid sequence to changes in cell organization during the evolution of new species. This will be the first study to compare PopZ networks between species that have large differences in sub-cellular organization, and will test the hypothesis that scaffold networks provide a relatively promiscuous binding surface that facilitates evolutionary change. This project also emphasizes broader impacts that extend beyond basic science. In creating a unique and interactive live cell microscopy exhibit at the Children's Museum of Cheyenne, the investigators will inspire future generations of scientists by impressing them with the inherent beauty of sub-cellular organization.