期刊
BIOCHEMISTRY
卷 55, 期 50, 页码 6981-6995出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.biochem.6b00940
关键词
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资金
- Precursory Research for Embryonic Science and Technology
- Japan Science and Technology Agency
- 4-1-8 Honcho Kawaguchi, Saitama [332-0012]
- Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, United States Department of Energy [DOE DE-SC0002395]
- National Science Foundation [MCB-1021725, MCB-1613022]
- [26702036]
- U.S. Department of Energy (DOE) [DE-SC0002395] Funding Source: U.S. Department of Energy (DOE)
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1613022] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [26702036] Funding Source: KAKEN
Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors that sense near-ultraviolet to far-red light. Like the distantly related phytochromes, all CBCRs reported to date have a conserved Cys residue (the canonical Cys or first Cys) that forms a thioether linkage to C3(1) of the linear tetrapyrrole (bilin) chromophore. Detection of ultraviolet, violet, and blue light is performed by at least three subfamilies of two-Cys CBCRs that require both the first Cys and a second Cys that forms a second covalent linkage to C10 of the bilin. In the well-characterized DXCF subfamily, the second Cys is part of a conserved Asp-Xaa-Cys-Phe motif. We here report novel CBCRs lacking the first Cys but retaining the DXCF Cys as part of a conserved Asp-Xaa-Cys-Ile-Pro (DXCIP) motif: Phylogenetic analysis demonstrates that DXCIP CBCRs are a sister to a lineage of DXCF CBCR domains from phototaxis sensors. Three such DXCIP CBCR domains (cce_4193g1, Cyan8802_2776g1, and JSC1_24240) were characterized after recombinant expression in Escherichia coli engineered to produce phycocyanobilin. All three covalently bound bilin and showed unidirectional photoconversion in response to green light. Spectra of acid-denatured proteins in the dark-adapted state do not correspond to those of known bilins. One DXCIP CBCR, cce_4193g1, exhibited very rapid dark reversion consistent with a function as a power sensor. However, Cyan8802_2776g1 exhibited slower dark reversion and would not have such a function. The full-length cce_4193 protein also possesses a DXCF CBCR GAF domain (cce_4193g2) with a covalently bound phycoviolobilin chromophore and a blue/green photocycle. Our studies indicate that CBCRs need not contain the canonical Cys residue to function as photochromic light sensors and that phototaxis proteins containing DXCIP CBCRs may potentially perceive both light quality and light intensity.
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