Structure, function and signalling in Cph1 and related phytochromes

光敏色素是植物发育的核心分子光开关，并且在许多微生物中已知。虽然植物光敏色素信号传导机制仍然知之甚少，但许多原核光敏色素是参与“双组分”磷酸传递信号传导的光调节感觉组氨酸蛋白激酶（SHPK）。蓝藻光敏色素Cph 1是一种SHPK，与植物光敏色素有许多相似之处，但更容易用于生物化学和生物物理研究-例如，允许我们通过X射线晶体学解决其感觉模块的3D结构。在这里，我们建议利用Cph 1研究光敏色素分子内信号的基础上的三维结构信息。光感受器分子将被设计成在光谱、色谱和酶测定的帮助下实验性地研究假定的信号过程。我们希望获得3D结构信息的光活化Pfr状态和全长Cph 1或类似的原核光敏色素。我们也希望获得植物光敏色素的结构数据。我们期望借此解释感觉组氨酸蛋白激酶的分子内调节机制，以及植物和蓝藻光敏色素之间的共同或不同机制。

Phytochromes are molecular photoswitches central to plant development and known in many microorganisms. While the plant phytochrome signalling mechanism is still poorly understood, many prokaryotic phytochromes are light-regulated sensory histidine protein kinases (SHPK's) involved in "two-component" phosphorelay signalling. The cyanobacterial phytochrome Cph1 is a SHPK with many similarities to plant phytochromes, but is much more accessible for biochemical and biophysical studies – for example, allowing us to solve the 3D structure of its sensory module by X-ray crystallography. Here we propose to exploit Cph1 to study phytochrome intramolecular signalling on the basis of 3D structural information. Photoreceptor molecules will be engineered to investigate putative signal processes experimentally with the help of spectroscopic, chromatographic and enzymatic assays. We hope to obtain 3D structural information about the photoactivated Pfr state and for full-length Cph1 or a similar prokaryotic phytochrome. We also hope to obtain structural data for plant phytochromes. We expect thereby to explain the intramolecular regulatory mechanism(s) of sensory histidine protein kinases and those common to or differing between plant and cyanobacterialphytochromes.