Understanding the Assembly of the Small Ribosomal Subunit in Bacteria

核糖体在细菌细胞中催化蛋白质合成。蛋白质是细胞结构的基石，也是进行维持生命所必需的生化反应的酶的基石。考虑到我们依赖细菌生产食品和生物燃料以及为加拿大人制造大量基本产品（抗生素、疫苗、酶和工业化学品等），必须充分了解细菌生理学的关键过程，包括核糖体的组装。核糖体由两个亚基（称为30S和50S）组成，含有50多个独立的成分，构成了生物体中最复杂的大分子机器之一。我们和其他人之前的研究已经发现了一些在30S亚基组装后期起作用的蛋白质因子，使其成熟成为一个非常有效的过程。然而，它们的作用机制尚未揭示。我们的研究计划旨在建立四个关键装配因子的功能模型，YjeQ, RbfA， RimM和Era。早期的研究表明，这些因素在30S亚基成熟的后期协同作用，它们构成了提高组装过程效率的主要蛋白质群。为此，我们正在获得缺乏这些因素的单基因缺失菌株积累的核糖体中间体的低温电镜结构，并将研究它们的结构相似性程度。总的来说，这些结构将确定YjeQ， RbfA， RimM和Era是否在相同或不同的组装阶段起作用。此外，我们将建立它们与30S核糖体亚基结合的具体顺序以及它们诱导的构象变化。随着项目的进展，我们将研究额外的装配因子如何辅助装配过程并调节YjeQ、RbfA、RimM和Era的功能。最终，我们的研究结果将描述使核糖体组装成为一个高效过程的事件序列。因此，它将使我们对生命的基本过程之一的理解向前迈出重要的一步。

The ribosome catalyzes protein synthesis in bacterial cells. Proteins are the building blocks for cellular structures and also for the enzymes that perform the biochemical reactions necessary to sustain life. Considering our dependency from bacteria for production of food and biofuels and for manufacturing a large number of basic products for Canadians (antibiotics, vaccines, enzymes and chemicals for industry, etc), it is essential that key processes of the bacterial physiology, including the assembly of the ribosome, are well understood. Made of two subunits (called 30S and 50S) and containing more than 50 individual components, the ribosome constitutes one of the most intricate macromolecular machines found in living organisms. Previous studies from others and us have identified a number of protein factors that act at the late stages of assembly of the 30S subunit, making its maturation an extremely efficient process. However, their mechanisms of action have not been revealed. Our research program is aimed at establishing a functional model for four critical assembly factors, YjeQ, RbfA, RimM and Era. Earlier studies suggested that these factors act in concert during the late stages of maturation of the 30S subunit and that they constitute the main group of proteins boosting the efficiency of the assembly process. To this end, we are obtaining the cryo-electron microscopy structure of ribosome intermediates accumulated by single-gene deletion strains lacking these factors and will study their degree of structural similarity. Collectively, these structures will establish whether YjeQ, RbfA, RimM and Era act in the same or different stages of assembly. In addition, we will establish the specific order in which they bind to the 30S ribosomal subunit and the conformational changes that they induce. As our program progresses, we will study how additional assembly factors also assist the process of assembly and tune the function of YjeQ, RbfA, RimM and Era. Ultimately, the outcome of our research will delineate the sequence of events that made ribosome assembly a highly efficient process. Consequently, it will constitute a significant step forward in our understanding of one of the essential processes for life.