Phytochromes are a widespread family of red/far-red responsive photoreceptors first discovered in plants, where they constitute one of the three main classes of photomorphogenesis regulators. All phytochromes utilize covalently attached bilin chromophores that enable photoconversion between red-absorbing (P(r)) and far-red-absorbing (P(fr)) forms. Phytochromes are thus photoswitchable photosensors; canonical phytochromes have a conserved N-terminal photosensory core and a C-terminal regulatory region, which typically includes a histidine-kinase-related domain. The discovery of new bacterial and cyanobacterial members of the phytochrome family within the last decade has greatly aided biochemical and structural characterization of this family, with the first crystal structure of a bacteriophytochrome photosensory core appearing in 2005. This structure and other recent biochemical studies have provided exciting new insights into the structure of phytochrome, the photoconversion process that is central to light sensing, and the mechanism of signal transfer by this important family of photoreceptors.

中文翻译：

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光敏色素结构和信号机制

光敏色素是一种广泛存在的红色/远红色响应光感受器家族，最初在植物中发现，它们构成了三大类光形态发生调节剂之一。所有光敏色素都利用共价连接的胆素发色团，使吸收红色 (P(r)) 和远红色吸收 (P(fr)) 形式之间的光转换成为可能。因此，光敏色素是可光切换的光电传感器；典型光敏色素具有保守的 N 端光敏核心和 C 端调节区，通常包括组氨酸激酶相关域。在过去十年中发现了光敏色素家族的新细菌和蓝藻成员，极大地帮助了该家族的生化和结构表征，2005 年出现了光敏色素光敏核心的第一个晶体结构。