Phytochrome proteins control the growth, reproduction, and photosynthesis of plants, fungi, and bacteria. Light is detected by a bilin cofactor, but it remains elusive how this leads to activation of the protein through structural changes. We present serial femtosecond X-ray crystallographic data of the chromophore-binding domains of a bacterial phytochrome at delay times of 1 ps and 10 ps after photoexcitation. The data reveal a twist of the D-ring, which leads to partial detachment of the chromophore from the protein. Unexpectedly, the conserved so-called pyrrole water is photodissociated from the chromophore, concomitant with movement of the A-ring and a key signalling aspartate. The changes are wired together by ultrafast backbone and water movements around the chromophore, channeling them into signal transduction towards the output domains. We suggest that the observed collective changes are important for the phytochrome photoresponse, explaining the earliest steps of how plants, fungi and bacteria sense red light.

中文翻译：

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飞秒X射线激光捕获的植物色素蛋白的主要结构光响应

植物色素蛋白控制着植物，真菌和细菌的生长，繁殖和光合作用。胆红素辅助因子可检测到光，但如何通过结构变化导致蛋白质活化仍然难以捉摸。我们提出了在光激发后1 ps和10 ps的延迟时间细菌荧光色素的发色团结合域的系列飞秒X射线晶体学数据。数据显示D环扭曲，导致发色团与蛋白质部分分离。出乎意料的是，守恒的所谓吡咯水与生色团发生光解离，并伴随着A环和关键信号天冬氨酸的移动。这些变化通过发色团周围的超快骨架和水运动连接在一起，将它们引导到信号转导到输出域。