现在，一种植物光敏色素的感光核心在静止状态和（图示）活跃状态下的晶体结构都已被确定。通过对来自“嗜极菌”Deinococcus radiodurans的植物光敏色素进行研究，Sebastian Westenhoff及同事发现，在静止状态和活跃状态间的转变是由与该生色团接触的一个保守的“舌头”介导的。该生色团附近原子尺度的结构变化在其通过这个“舌头”向其他地方传播时被放大，最后产生一个馈送到细胞信号作用网络其余部分的纳米尺度的构形信号。
Sensory proteins must relay structural signals from the sensory site over large distances to regulatory output domains. Phytochromes are a major family of red-light-sensing kinases that control diverse cellular functions in plants, bacteria and fungi. Bacterial phytochromes consist of a photosensory core and a carboxy-terminal regulatory domain. Structures of photosensory cores are reported in the resting state and conformational responses to light activation have been proposed in the vicinity of the chromophore. However, the structure of the signalling state and the mechanism of downstream signal relay through the photosensory core remain elusive. Here we report crystal and solution structures of the resting and activated states of the photosensory core of the bacteriophytochrome from Deinococcus radiodurans. The structures show an open and closed form of the dimeric protein for the activated and resting states, respectively. This nanometre-scale rearrangement is controlled by refolding of an evolutionarily conserved ‘tongue’, which is in contact with the chromophore. The findings reveal an unusual mechanism in which atomic-scale conformational changes around the chromophore are first amplified into an ångstrom-scale distance change in the tongue, and further grow into a nanometre-scale conformational signal. The structural mechanism is a blueprint for understanding how phytochromes connect to the cellular signalling network.