PDF(Pubmed)
Abstract：
Certain cyanobacteria alter their photosynthetic light absorption between green and red, a phenomenon called complementary chromatic acclimation. The acclimation is regulated by a cyanobacteriochrome-class photosensor that reversibly photoconverts between green-absorbing (Pg) and red-absorbing (Pr) states. Here, we elucidated the structural basis of the green/red photocycle. In the Pg state, the bilin chromophore adopted the extended C15-Z,anti structure within a hydrophobic pocket. Upon photoconversion to the Pr state, the bilin is isomerized to the cyclic C15-E,syn structure, forming a water channel in the pocket. The solvation/desolvation of the bilin causes changes in the protonation state and the stability of π-conjugation at the B ring, leading to a large absorption shift. These results advance our understanding of the enormous spectral diversity of the phytochrome superfamily.
摘要：
某些蓝细菌改变了它们在绿色和红色之间的光合光吸收，一种叫做互补色适应的现象。适应由蓝藻色类光电传感器调节，该传感器在绿色吸收（Pg）和红色吸收（Pr）状态之间可逆地进行光转换。这里,我们阐明了绿色/红色光循环的结构基础。在PG状态下，bilin发色团采用了扩展的C15-Z，疏水口袋内的反结构。在光转换为Pr状态时，Bilin异构化为环状C15-E，syn结构，在口袋里形成一条水道。bilin的溶剂化/去溶剂化导致质子化状态的变化和B环上π-共轭的稳定性，导致大的吸收偏移。这些结果促进了我们对植物色素超家族的巨大光谱多样性的理解。
