Identification of Cyanobacteriochromes Detecting Far-Red Light.
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.
Department of Molecular and Cellular Biology, University of California , Davis, California 95616, United States.
Nathan C
NC
Rockwell
Department of Molecular and Cellular Biology, University of California , Davis, California 95616, United States.
Shelley S
SS
Martin
Department of Molecular and Cellular Biology, University of California , Davis, California 95616, United States.
J Clark
JC
Lagarias
D065966:Absorption, Physicochemical; D003116:Color; D000458:Cyanobacteria; D008027:Light; D010834:Phytochrome / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D010834:Phytochrome