Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany.
Biochemistry and Functional Proteomics, Institute of Biology II, University of Freiburg, Freiburg, Germany.
Elife. 2021 Dec 31;10:e68213. doi: 10.7554/eLife.68213.
Human mitochondria express a genome that encodes thirteen core subunits of the oxidative phosphorylation system (OXPHOS). These proteins insert into the inner membrane co-translationally. Therefore, mitochondrial ribosomes engage with the OXA1L-insertase and membrane-associated proteins, which support membrane insertion of translation products and early assembly steps into OXPHOS complexes. To identify ribosome-associated biogenesis factors for the OXPHOS system, we purified ribosomes and associated proteins from mitochondria. We identified TMEM223 as a ribosome-associated protein involved in complex IV biogenesis. TMEM223 stimulates the translation of COX1 mRNA and is a constituent of early COX1 assembly intermediates. Moreover, we show that SMIM4 together with C12ORF73 interacts with newly synthesized cytochrome to support initial steps of complex III biogenesis in complex with UQCC1 and UQCC2. Our analyses define the interactome of the human mitochondrial ribosome and reveal novel assembly factors for complex III and IV biogenesis that link early assembly stages to the translation machinery.
人类线粒体表达一个基因组，该基因组编码氧化磷酸化系统 (OXPHOS) 的十三个核心亚基。这些蛋白质在共翻译过程中插入内膜。因此，线粒体核糖体与 OXA1L-插入酶和膜相关蛋白结合，这些蛋白支持翻译产物的膜插入和早期组装步骤进入 OXPHOS 复合物。为了鉴定 OXPHOS 系统的核糖体相关生物发生因子，我们从线粒体中纯化了核糖体和相关蛋白。我们发现 TMEM223 是一种与复合物 IV 生物发生相关的核糖体相关蛋白。TMEM223 刺激 COX1 mRNA 的翻译，并且是早期 COX1 组装中间产物的组成部分。此外，我们表明 SMIM4 与 C12ORF73 一起与新合成的细胞色素相互作用，以支持与 UQCC1 和 UQCC2 结合的复合物 III 生物发生的初始步骤。我们的分析定义了人类线粒体核糖体的相互作用组，并揭示了与复合物 III 和 IV 生物发生相关的新组装因子，这些因子将早期组装阶段与翻译机制联系起来。
