Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 295, Issue 19, Pages 6754-6766Publisher
ELSEVIER
DOI: 10.1074/jbc.RA120.012950
Keywords
cyanobacteria; plant; algae; photosynthesis; photoreceptor; Color sensing; dual cysteine phytochromes; phycocyanobilin; protochromism; violet and blue light photoreceptors
Categories
Funding
- Next-Generation BioGreen 21 Program, Rural Development Administration [PJ013118]
- KIST Open Research Program [2E27512-17-122]
- Ministry of Oceans and Fisheries Grant, Korea [20180430]
- National Institutes of Health [R01 GM068552]
- United States Department of Agriculture National Institute of Food and Agriculture Hatch project [CA-D*-MCB-4126-H]
- Chemical Sciences, Geosciences, and the Biosciences Division, Office of Basic Energy Sciences, Office of Science, United States Department of Energy [DE-FG02-09ER16117]
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The atypical trichromatic cyanobacterial phytochrome NpTP1 from Nostoc punctiforme ATCC 29133 is a linear tetrapyrrole (bilin)-binding photoreceptor protein that possesses tandem-cysteine residues responsible for shifting its light-sensing maximum to the violet spectral region. Using bioinformatics and phylogenetic analyses, here we established that tandem-cysteine cyanobacterial phytochromes (TCCPs) compose a well-supported monophyletic phytochrome lineage distinct from prototypical red/far-red cyanobacterial phytochromes. To investigate the light-sensing diversity of this family, we compared the spectroscopic properties of NpTP1 (here renamed NpTCCP) with those of three phylogenetically diverged TCCPs identified in the draft genomes of Tolypothrix sp. PCC7910, Scytonema sp. PCC10023, and Gloeocapsa sp. PCC7513. Recombinant photosensory core modules of ToTCCP, ScTCCP, and GlTCCP exhibited violet-blue?absorbing dark-states consistent with dual thioether-linked phycocyanobilin (PCB) chromophores. Photoexcitation generated singly-linked photoproduct mixtures with variable ratios of yellow-orange and red-absorbing species. The photoproduct ratio was strongly influenced by pH and by mutagenesis of TCCP- and phytochrome-specific signature residues. Our experiments support the conclusion that both photoproduct species possess protonated 15E bilin chromophores, but differ in the ionization state of the noncanonical ?second? cysteine sulfhydryl group. We found that the ionization state of this and other residues influences subsequent conformational change and downstream signal transmission. We also show that tandem-cysteine phytochromes present in eukaryotes possess similar amino acid substitutions within their chromophore-binding pocket, which tune their spectral properties in an analogous fashion. Taken together, our findings provide a roadmap for tailoring the wavelength specificity of plant phytochromes to optimize plant performance in diverse natural and artificial light environments.
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