美国耶鲁大学张凯等研究人员合作解析哺乳动物呼吸系统超级复合物的高分辨率原位结构。2024年5月29日，《自然》杂志在线发表了这项成果。

研究人员使用原位冷冻电镜方法直接对猪的线粒体进行成像。这使其能够确定呼吸超级复合物在天然状态下的各种高阶组装结构。研究人员确定了四种主要的超级复合物组织：I₁III₂IV₁、I₁III₂IV₂、I₂III₂IV₂和I₂III₄IV₂，它们有可能在内膜上扩展成更高阶的阵列。这些不同的超级复合体主要是由“蛋白质-脂质-蛋白质”相互作用形成的，而这反过来又对周围膜的局部几何形状产生重大影响。

这些原位结构还捕获了这些呼吸超级复合物中的大量反应性中间产物，揭示了复合物I中泛醌/泛醇交换机制和复合物III中Q循环的动态过程。对在不同条件下处理的线粒体超级复合物进行的结构比较表明，复合物I和复合物III的构象状态之间可能存在相关性，这可能是对环境变化的反应。通过保留原生膜环境，该方法实现了线粒体呼吸超级复合物反应结构研究的高分辨率、多尺度，从原子级细节到更广泛的亚细胞背景。

据了解，线粒体在通过氧化磷酸化产生ATP能量的过程中起着举足轻重的作用，氧化磷酸化是通过一系列呼吸复合体在内膜上进行的。尽管进行了广泛的体外结构研究，但确定其生理状态下分子机制的原子细节仍是一项重大挑战，这主要是因为在纯化过程中失去了天然环境。

附：英文原文

Title: High-resolution in situ structures of mammalian respiratory supercomplexes

Author: Zheng, Wan, Chai, Pengxin, Zhu, Jiapeng, Zhang, Kai

Issue&Volume: 2024-05-29

Abstract: Mitochondria play a pivotal part in ATP energy production through oxidative phosphorylation, which occurs within the inner membrane through a series of respiratory complexes1,2,3,4. Despite extensive in vitro structural studies, determining the atomic details of their molecular mechanisms in physiological states remains a major challenge, primarily because of loss of the native environment during purification. Here we directly image porcine mitochondria using an in situ cryo-electron microscopy approach. This enables us to determine the structures of various high-order assemblies of respiratory supercomplexes in their native states. We identify four main supercomplex organizations: I1III2IV1, I1III2IV2, I2III2IV2 and I2III4IV2, which potentially expand into higher-order arrays on the inner membranes. These diverse supercomplexes are largely formed by ‘protein–lipids–protein’ interactions, which in turn have a substantial impact on the local geometry of the surrounding membranes. Our in situ structures also capture numerous reactive intermediates within these respiratory supercomplexes, shedding light on the dynamic processes of the ubiquinone/ubiquinol exchange mechanism in complex I and the Q-cycle in complex III. Structural comparison of supercomplexes from mitochondria treated under different conditions indicates a possible correlation between conformational states of complexes I and III, probably in response to environmental changes. By preserving the native membrane environment, our approach enables structural studies of mitochondrial respiratory supercomplexes in reaction at high resolution across multiple scales, from atomic-level details to the broader subcellular context.

DOI: 10.1038/s41586-024-07488-9

Source: https://www.nature.com/articles/s41586-024-07488-9