Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden.
Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Ceske Budejovice, Czech Republic.
EMBO J. 2021 Mar 15;40(6):e106292. doi: 10.15252/embj.2020106292. Epub 2021 Feb 12.
Mitoribosomes consist of ribosomal RNA and protein components, coordinated assembly of which is critical for function. We used mitoribosomes from Trypanosoma brucei with reduced RNA and increased protein mass to provide insights into the biogenesis of the mitoribosomal large subunit. Structural characterization of a stable assembly intermediate revealed 22 assembly factors, some of which have orthologues/counterparts/homologues in mammalian genomes. These assembly factors form a protein network that spans a distance of 180 Å, shielding the ribosomal RNA surface. The central protuberance and L7/L12 stalk are not assembled entirely and require removal of assembly factors and remodeling of the mitoribosomal proteins to become functional. The conserved proteins GTPBP7 and mt-EngA are bound together at the subunit interface in proximity to the peptidyl transferase center. A mitochondrial acyl-carrier protein plays a role in docking the L1 stalk, which needs to be repositioned during maturation. Additional enzymatically deactivated factors scaffold the assembly while the exit tunnel is blocked. Together, this extensive network of accessory factors stabilizes the immature sites and connects the functionally important regions of the mitoribosomal large subunit.
线粒体核糖体由核糖体 RNA 和蛋白质组成，其协调组装对于功能至关重要。我们使用 RNA 减少而蛋白质质量增加的布氏锥虫线粒体核糖体，以深入了解线粒体核糖体大亚基的生物发生。稳定组装中间产物的结构特征揭示了 22 种组装因子，其中一些在哺乳动物基因组中具有同源物/对应物/同源物。这些组装因子形成一个跨越 180Å 的蛋白质网络，屏蔽核糖体 RNA 表面。中央隆起和 L7/L12 柄部并未完全组装，需要去除组装因子并重塑线粒体核糖体蛋白才能发挥功能。保守蛋白 GTPBP7 和 mt-EngA 在亚基界面上结合在一起，靠近肽基转移酶中心。一种线粒体酰基载体蛋白在 L1 柄部的对接中发挥作用，该柄部在成熟过程中需要重新定位。额外的酶失活因子支架组装，同时出口隧道被阻塞。总的来说，这种广泛的辅助因子网络稳定了不成熟的部位，并连接了线粒体核糖体大亚基的功能重要区域。
