Identification of Cyanobacteriochromes Detecting Far-Red Light

Biochemistry. 2016 Jul 19;55(28):3907-19. doi: 10.1021/acs.biochem.6b00299. Epub 2016 Jul 2.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Absorption, Physicochemical
  • Color
  • Cyanobacteria*
  • Light*
  • Phytochrome / chemistry
  • Phytochrome / metabolism*
  • Spectrometry, Fluorescence

Substances

  • Phytochrome