Rockwell Nathan C, Martin Shelley S, Lagarias J Clark
Department of Molecular and Cellular Biology, University of California , Davis, California 95616, United States.
Biochemistry. 2016 Jul 19;55(28):3907-19. doi: 10.1021/acs.biochem.6b00299. Epub 2016 Jul 2.
The opacity of mammalian tissue to visible light and the strong attenuation of infrared light by water at ≥900 nm have contributed to growing interest in the development of far-red and near-infrared absorbing tools for visualizing and actuating responses within live cells. Here we report the discovery of cyanobacteriochromes (CBCRs) responsive to light in this far-red window. CBCRs are linear tetrapyrrole (bilin)-based light sensors distantly related to plant phytochrome sensors. Our studies reveal far-red (λmax = 725-755 nm)/orange (λmax = 590-600 nm) and far-red/red (λmax = 615-685 nm) photoswitches that are small (<200 amino acids) and can be genetically reconstituted in living cells. Phylogenetic analysis and characterization of additional CBCRs demonstrated that far-red/orange CBCRs evolved after a complex transition from green/red CBCRs known for regulating complementary chromatic acclimation. Incorporation of different bilin chromophores demonstrated that tuning mechanisms responsible for red-shifted chromophore absorption act at the A-, B-, and/or C-rings, whereas photoisomerization occurs at the D-ring. Two such proteins exhibited detectable fluorescence extending well into the near-infrared region. This work extends the spectral window of CBCRs to the edge of the infrared, raising the possibility of using CBCRs in synthetic biology applications in the far-red region of the spectrum.
哺乳动物组织对可见光的不透明度以及水在≥900 nm处对红外光的强烈衰减，促使人们对开发用于可视化和激活活细胞内反应的远红和近红外吸收工具越来越感兴趣。在此，我们报告了在这个远红窗口中对光有响应的蓝细菌视色素（CBCRs）的发现。CBCRs是基于线性四吡咯（胆色素）的光传感器，与植物光敏色素传感器有较远的亲缘关系。我们的研究揭示了小型（<200个氨基酸）的远红（λmax = 725 - 755 nm）/橙色（λmax = 590 - 600 nm）和远红/红色（λmax = 615 - 685 nm）光开关，它们可以在活细胞中进行基因重组。对其他CBCRs的系统发育分析和表征表明，远红/橙色CBCRs是在从以调节互补色适应而闻名的绿色/红色CBCRs经历复杂转变后进化而来的。不同胆色素发色团的掺入表明，负责红移发色团吸收的调谐机制作用于A、B和/或C环，而光异构化发生在D环。两种这样的蛋白质表现出可检测到的荧光，延伸到近红外区域。这项工作将CBCRs的光谱窗口扩展到红外边缘，增加了在光谱的远红区域将CBCRs用于合成生物学应用的可能性。
