Nanoscience Center, Department of Physics, University of Jyvaskyla, 40014, Jyvaskyla, Finland.
Research and Innovation Services, Tampere University, 33014, Tampere, Finland.
Photochem Photobiol Sci. 2022 Nov;21(11):1975-1989. doi: 10.1007/s43630-022-00272-6. Epub 2022 Jul 29.
Phytochromes are red light-sensing photoreceptor proteins that bind a bilin chromophore. Here, we investigate the role of a conserved histidine (H260) and tyrosine (Y263) in the chromophore-binding domain (CBD) of Deinococcus radiodurans phytochrome (DrBphP). Using crystallography, we show that in the H260A variant, the missing imidazole side chain leads to increased water content in the binding pocket. On the other hand, Y263F mutation reduces the water occupancy around the chromophore. Together, these changes in water coordination alter the protonation and spectroscopic properties of the biliverdin. These results pinpoint the importance of this conserved histidine and tyrosine, and the related water network, for the function and applications of phytochromes.
光敏色素是一种结合双吡咯发色团的红光感应光受体蛋白。在这里，我们研究了在耐辐射球菌光敏色素（DrBphP）的发色团结合域（CBD）中保守组氨酸（H260）和酪氨酸（Y263）的作用。通过晶体学研究，我们发现在 H260A 变体中，缺失的咪唑侧链导致结合口袋中增加了水含量。另一方面，Y263F 突变减少了发色团周围的水占有率。总的来说，这些水配位的变化改变了胆红素的质子化和光谱性质。这些结果指出了这个保守的组氨酸和酪氨酸以及相关的水网络对于光敏色素的功能和应用的重要性。
