Department of Chemistry and Molecular Biology, University of Gothenburg, 405 30 Göteborg, Sweden; Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, 405 30 Göteborg, Sweden.
Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, 405 30 Göteborg, Sweden; Department of Psychiatry and Neurochemistry, University of Gothenburg, 405 30 Göteborg, Sweden.
J Struct Biol. 2023 Sep;215(3):108008. doi: 10.1016/j.jsb.2023.108008. Epub 2023 Aug 3.
Mitochondria are essential organelles that produce most of the energy via the oxidative phosphorylation (OXPHOS) system in all eukaryotic cells. Several essential subunits of the OXPHOS system are encoded by the mitochondrial genome (mtDNA) despite its small size. Defects in mtDNA maintenance and expression can lead to severe OXPHOS deficiencies and are amongst the most common causes of mitochondrial disease. The mtDNA is packaged as nucleoprotein structures, referred to as nucleoids. The conserved mitochondrial proteins, ARS-binding factor 2 (Abf2) in the budding yeast Saccharomyces cerevisiae (S. cerevisiae) and mitochondrial transcription factor A (TFAM) in mammals, are nucleoid associated proteins (NAPs) acting as condensing factors needed for packaging and maintenance of the mtDNA. Interestingly, gene knockout of Abf2 leads, in yeast, to the loss of mtDNA and respiratory growth, providing evidence for its crucial role. On a structural level, the condensing factors usually contain two DNA binding domains called high-mobility group boxes (HMG boxes). The co-operating mechanical activities of these domains are crucial in establishing the nucleoid architecture by bending the DNA strands. Here we used advanced solution NMR spectroscopy methods to characterize the dynamical properties of Abf2 together with its interaction with DNA. We find that the two HMG-domains react notably different to external cues like temperature and salt, indicating distinct functional properties. Biophysical characterizations show the pronounced difference of these domains upon DNA-binding, suggesting a refined picture of the Abf2 functional cycle.
线粒体是产生能量的重要细胞器，通过所有真核细胞中的氧化磷酸化（OXPHOS）系统产生大部分能量。尽管线粒体基因组（mtDNA）很小，但 OXPHOS 系统的几个基本亚基是由线粒体基因组编码的。mtDNA 维持和表达的缺陷可导致严重的 OXPHOS 缺乏，是线粒体疾病最常见的原因之一。mtDNA 被包装为核蛋白结构，称为核体。在酿酒酵母（Saccharomyces cerevisiae）中，保守的线粒体蛋白 ARS 结合因子 2（Abf2）和哺乳动物中的线粒体转录因子 A（TFAM）是与核体相关的蛋白（NAPs），作为包装和维持 mtDNA 所需的浓缩因子发挥作用。有趣的是，Abf2 的基因敲除会导致酵母失去 mtDNA 和呼吸生长，这为其关键作用提供了证据。在结构水平上，浓缩因子通常包含两个称为高迁移率族盒（HMG 盒）的 DNA 结合结构域。这些结构域的协同机械活动对于通过弯曲 DNA 链来建立核体结构至关重要。在这里，我们使用先进的溶液 NMR 光谱方法来表征 Abf2 及其与 DNA 的相互作用的动力学特性。我们发现，两个 HMG 结构域对温度和盐等外部线索的反应明显不同，表明其具有不同的功能特性。生物物理特性表明，这些结构域在 DNA 结合时存在显著差异，这表明 Abf2 功能循环的图片更加精细。
