Arpin Dominic, Palacios Armando, Basu Kaustuv, Ortega Joaquin
Department of Anatomy and Cell Biology, McGill University, 3640 Rue University, Montreal, Quebec H3A 0C7, Canada.
Centre de Recherche en Biologie Structurale, McGill University, 3649 Promenade Sir William Osler, Montreal, QuebecH3G 0B1, Canada.
Nucleic Acids Res. 2025 Jan 11;53(2). doi: 10.1093/nar/gkae1197.
The intricate process of 50S ribosomal subunit assembly in Bacillus subtilis involves multiple parallel pathways converging into a crucial intermediate known as the 45S particle. RbgA and YphC, play pivotal roles in completing the maturation of the functional sites in the 45S particle. In this work, we found that RbgA and YphC can independently bind the 45S particle with high affinity, but when RbgA binds first to the particle, it significantly increases the binding affinity of YphC. Using cryo-electron microscopy, we determined that the changes exerted by RbgA and YphC when binding independently closely resemble those observed when the two factors bind to the 45S particle simultaneously. However, the structural analysis revealed that RbgA binding causes a conformational change that uncovers the binding site for YphC, thus increasing its binding affinity. We concluded that the functional interplay between RbgA and YphC primarily revolves around one factor promoting the binding of the other, rather than the binding of the two factors inducing entirely new conformational changes compared with those induced by the factors individually. These results highlight the synergic mechanism between two essential assembly factors, underscoring the intricate mechanism bacteria use to maximize the efficiency of the ribosome assembly process.
枯草芽孢杆菌中50S核糖体亚基的复杂组装过程涉及多条平行途径汇聚成一个关键中间体，即所谓的45S颗粒。RbgA和YphC在完成45S颗粒功能位点的成熟过程中发挥着关键作用。在这项研究中，我们发现RbgA和YphC能够以高亲和力独立结合45S颗粒，但当RbgA首先与颗粒结合时，它会显著增加YphC的结合亲和力。利用冷冻电子显微镜，我们确定了RbgA和YphC独立结合时所产生的变化与这两个因子同时结合到45S颗粒时所观察到的变化非常相似。然而，结构分析表明，RbgA的结合会引起构象变化，从而暴露出YphC的结合位点，进而增加其结合亲和力。我们得出结论，RbgA和YphC之间的功能相互作用主要围绕一个因子促进另一个因子的结合，而不是与单个因子诱导的构象变化相比，两个因子的结合诱导全新的构象变化。这些结果突出了两个关键组装因子之间的协同机制，强调了细菌用于最大化核糖体组装过程效率的复杂机制。
