Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651, USA.
Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651, USA.
Cell Rep. 2018 Feb 13;22(7):1935-1944. doi: 10.1016/j.celrep.2018.01.066.
Mammalian mtDNA encodes only 13 proteins, all essential components of respiratory complexes, synthesized by mitochondrial ribosomes. Mitoribosomes contain greatly truncated RNAs transcribed from mtDNA, including a structural tRNA in place of 5S RNA as a scaffold for binding 82 nucleus-encoded proteins, mitoribosomal proteins (MRPs). Cryoelectron microscopy (cryo-EM) studies have determined the structure of the mitoribosome, but its mechanism of assembly is unknown. Our SILAC pulse-labeling experiments determine the rates of mitochondrial import of MRPs and their assembly into intact mitoribosomes, providing a basis for distinguishing MRPs that bind at early and late stages in mitoribosome assembly to generate a working model for mitoribosome assembly. Mitoribosome assembly is a slow process initiated at the mtDNA nucleoid driven by excess synthesis of individual MRPs. MRPs that are tightly associated in the structure frequently join the complex in a coordinated manner. Clinically significant MRP mutations reported to date affect proteins that bind early on during assembly.
哺乳动物的 mtDNA 仅编码 13 种蛋白质，它们都是线粒体核糖体合成的呼吸复合物的必需成分。线粒体核糖体包含从 mtDNA 转录的大大截断的 RNA，包括一种结构 tRNA 代替 5S RNA 作为结合 82 种核编码蛋白质（线粒体核糖体蛋白，MRP）的支架。冷冻电子显微镜（cryo-EM）研究已经确定了线粒体核糖体的结构，但它的组装机制尚不清楚。我们的 SILAC 脉冲标记实验确定了 MRP 的线粒体导入率及其组装成完整的线粒体核糖体的速率，为区分在早期和晚期结合到线粒体核糖体组装中的 MRP 提供了基础，从而为线粒体核糖体组装生成了一个工作模型。线粒体核糖体的组装是一个由 mtDNA 核体驱动的、由单个 MRP 过量合成引发的缓慢过程。在结构中紧密结合的 MRP 通常以协调的方式加入复合物。迄今为止报道的具有临床意义的 MRP 突变影响在组装过程中早期结合的蛋白质。
