Cytochrome c oxidase catalyses the reduction of molecular oxygen to water while the energy released in this process is used to pump protons across a biological membrane. Although an extremely well-studied biological system, the molecular mechanism of proton pumping by cytochrome c oxidase is still not understood. Here we report a method to produce large quantities of highly diffracting microcrystals of ba ₃-type cytochrome c oxidase from Thermus thermophilus suitable for serial femtosecond crystallography. The room-temperature structure of cytochrome c oxidase is solved to 2.3 Å resolution from data collected at an X-ray Free Electron Laser. We find overall agreement with earlier X-ray structures solved from diffraction data collected at cryogenic temperature. Previous structures solved from synchrotron radiation data, however, have shown conflicting results regarding the identity of the active-site ligand. Our room-temperature structure, which is free from the effects of radiation damage, reveals that a single-oxygen species in the form of a water molecule or hydroxide ion is bound in the active site. Structural differences between the ba ₃-type and aa ₃-type cytochrome c oxidases around the proton-loading site are also described.

中文翻译：

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在室温下细胞色素C氧化酶的系列飞秒晶体学结构。

细胞色素c氧化酶催化分子氧还原为水，而在此过程中释放的能量用于将质子泵送穿过生物膜。尽管对生物系统的研究非常深入，但仍不清楚细胞色素C氧化酶对质子泵入的分子机制。在这里，我们报告了一种生产大量ba ₃的高衍射微晶的方法嗜热栖热菌（Thermus thermophilus）的B型细胞色素C氧化酶适用于连续飞秒晶体学。细胞色素c氧化酶的室温结构从X射线自由电子激光器收集的数据解析为2.3Å分辨率。我们发现，与从低温温度收集的衍射数据解决的早期X射线结构完全一致。然而，从同步加速器辐射数据解析的先前结构已经显示出关于活性位点配体身份的矛盾结果。我们的室温结构不受辐射损伤的影响，它揭示了以水分子或氢氧根离子形式存在的单个氧分子结合在活性位点上。ba ₃型和aa ₃型之间的结构差异还描述了质子加载位点周围的2型细胞色素C氧化酶。