Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg 40530, Sweden.
Phys Chem Chem Phys. 2020 May 7;22(17):9195-9203. doi: 10.1039/c9cp06995j. Epub 2020 Mar 9.
Phytochromes are photosensory proteins in plants, fungi, and bacteria, which detect red- and far-red light. They undergo a transition between the resting (Pr) and photoactivated (Pfr) states. In bacterial phytochromes, the Pr-to-Pfr transition is facilitated by two intermediate states, called Lumi-R and Meta-R. The molecular structures of the protein in these states are not known and the molecular mechanism of photoconversion is not understood. Here, we apply transient infrared absorption spectroscopy to study the photocycle of the wild-type and Y263F mutant of the phytochrome from Deinococcus radiodurans (DrBphP) from nano- to milliseconds. We identify two sequentially forming Lumi-R states which differ in the local structure surrounding the carbonyl group of the biliverdin D-ring. We also find that the tyrosine at position 263 alters local structure and dynamics around the D-ring and causes an increased rate of Pfr formation. The results shed new light on the mechanism of light-signalling in phytochrome proteins.
植物、真菌和细菌中的光色素是感光蛋白，可检测红光和远红光。它们在静止（Pr）和光激活（Pfr）状态之间发生转变。在细菌光色素中，Pr 到 Pfr 的转变由两种中间状态（称为 Lumi-R 和 Meta-R）促进。这些状态下的蛋白质的分子结构尚不清楚，光转化的分子机制也不了解。在这里，我们应用瞬态红外吸收光谱技术，从纳秒到毫秒时间尺度研究来自耐辐射球菌的光色素（DrBphP）的野生型和 Y263F 突变体的光循环。我们确定了两个依次形成的 Lumi-R 状态，它们在胆红素 D-环羰基周围的局部结构上有所不同。我们还发现，位置 263 的酪氨酸改变了 D-环周围的局部结构和动力学，并导致 Pfr 形成速率增加。这些结果为光色素蛋白中的光信号转导机制提供了新的认识。
