Single-particle electron cryomicroscopy (cryo-EM) has led to a revolution in structural work on mammalian respiratory complex I. Complex I (mitochondrial NADH:ubiquinone oxidoreductase), a membrane-bound redox-driven proton pump, is one of the largest and most complicated enzymes in the mammalian cell. Rapid progress, following the first 5-Å resolution data on bovine complex I in 2014, has led to a model for mouse complex I at 3.3-Å resolution that contains 96% of the 8,518 residues and to the identification of different particle classes, some of which are assigned to biochemically defined states. Factors that helped improve resolution, including improvements to biochemistry, cryo-EM grid preparation, data collection strategy, and image processing, are discussed. Together with recent structural data from an ancient relative, membrane-bound hydrogenase, cryo-EM on mammalian complex I has provided new insights into the proton-pumping machinery and a foundation for understanding the enzyme's catalytic mechanism.

中文翻译：

---

哺乳动物呼吸复合体I通过低温EM镜头。

单粒子电子低温显微镜（cryo-EM）引发了哺乳动物呼吸系统复合物I的结构工作革命。复合物I（线粒体NADH：泛醌氧化还原酶）是一种膜结合的氧化还原驱动质子泵，是规模最大，应用最广泛的一种。哺乳动物细胞中最复杂的酶。继2014年关于牛复合物I的第​​一个5Å分辨率数据之后，快速的进展已导致建立了3.3Å分辨率的小鼠复合物I模型，该模型包含8,518个残基中的96％，并鉴定出不同的颗粒类别，其中一些其中的一些被分配到生化定义的状态。讨论了有助于提高分辨率的因素，包括对生物化学，冷冻-EM网格制备，数据收集策略和图像处理的改进。再加上古代亲戚的最新结构数据，