Cardiovascular Metabolic Disorders Program, Duke-NUS Medical School, Singapore, Singapore.
Department of Biochemistry and Molecular Biology, The Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Melbourne, Australia.
Nat Commun. 2020 Mar 11;11(1):1312. doi: 10.1038/s41467-020-14999-2.
The emergence of small open reading frame (sORF)-encoded peptides (SEPs) is rapidly expanding the known proteome at the lower end of the size distribution. Here, we show that the mitochondrial proteome, particularly the respiratory chain, is enriched for small proteins. Using a prediction and validation pipeline for SEPs, we report the discovery of 16 endogenous nuclear encoded, mitochondrial-localized SEPs (mito-SEPs). Through functional prediction, proteomics, metabolomics and metabolic flux modeling, we demonstrate that BRAWNIN, a 71 a.a. peptide encoded by C12orf73, is essential for respiratory chain complex III (CIII) assembly. In human cells, BRAWNIN is induced by the energy-sensing AMPK pathway, and its depletion impairs mitochondrial ATP production. In zebrafish, Brawnin deletion causes complete CIII loss, resulting in severe growth retardation, lactic acidosis and early death. Our findings demonstrate that BRAWNIN is essential for vertebrate oxidative phosphorylation. We propose that mito-SEPs are an untapped resource for essential regulators of oxidative metabolism.
小分子开放阅读框 (sORF) 编码肽 (SEPs) 的出现迅速扩大了已知的在尺寸分布低端的蛋白质组。在这里，我们表明线粒体蛋白质组，特别是呼吸链，富含小蛋白。通过 SEPs 的预测和验证管道，我们报告了 16 种内源性核编码、线粒体定位的 SEPs (mito-SEPs) 的发现。通过功能预测、蛋白质组学、代谢组学和代谢通量建模，我们证明了由 C12orf73 编码的 71 个氨基酸的肽 BRAWNIN 对于呼吸链复合物 III (CIII) 的组装是必不可少的。在人类细胞中，BRAWNIN 被能量感应 AMPK 途径诱导，其耗竭会损害线粒体 ATP 的产生。在斑马鱼中，Brawnin 的缺失导致 CIII 的完全丧失，从而导致严重的生长迟缓、乳酸酸中毒和早期死亡。我们的研究结果表明 BRAWNIN 对脊椎动物的氧化磷酸化是必不可少的。我们提出，mito-SEPs 是氧化代谢必需调节剂的未开发资源。
