Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK.
Biochim Biophys Acta Bioenerg. 2022 Oct 1;1863(7):148591. doi: 10.1016/j.bbabio.2022.148591. Epub 2022 Jul 14.
In mitochondria, complex IV (CIV) can be found as a monomer, a dimer or in association with other respiratory complexes. The atomic structure of the yeast S. cerevisiae CIV in a supercomplex (SC) with complex III (CIII) pointed to a region of significant conformational changes compared to the homologous mammalian CIV structures. These changes involved the matrix side domain of Cox5A at the CIII-CIV interface, and it was suggested that it could be required for SC formation. To investigate this, we solved the structure of the isolated monomeric CIV from S. cerevisiae stabilised in amphipol A8-35 at 3.9 Å using cryo-electron microscopy. Only a minor change in flexibility was seen in this Cox5A region, ruling out large CIV conformational shift for interaction with CIII and confirming the different fold of the yeast Cox5A subunit compared to mammalian homologues. Other differences in structure were the absence of two canonical subunits, Cox12 and Cox13, as well as Cox26, which is unique to the yeast CIV. Their absence is most likely due to the protein purification protocol used to isolate CIV from the III-IV SC.
在线粒体中，复合物 IV（CIV）可以以单体、二聚体或与其他呼吸复合物结合的形式存在。与同源哺乳动物 CIV 结构相比，酵母 S. cerevisiae CIV 在与复合物 III（CIII）的超复合物（SC）中的原子结构显示出明显的构象变化区域。这些变化涉及到 CIII-CIV 界面处 Cox5A 的基质侧结构域，并且有人认为这可能是 SC 形成所必需的。为了研究这一点，我们使用冷冻电镜在 3.9Å 分辨率下解析了稳定在 Amphipol A8-35 中的来自 S. cerevisiae 的分离单体 CIV 的结构。在这个 Cox5A 区域只观察到了微小的灵活性变化，排除了与 CIII 相互作用时 CIV 构象的大转变，并证实了酵母 Cox5A 亚基与哺乳动物同源物的不同折叠。结构上的其他差异是缺少两个典型的亚基 Cox12 和 Cox13，以及酵母 CIV 特有的 Cox26。它们的缺失很可能是由于用于从 III-IV SC 中分离 CIV 的蛋白纯化方案所致。
