A novel photoactive GAF domain of cyanobacteriochrome AnPixJ that shows reversible green/red photoconversion |
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Authors: | Narikawa Rei Fukushima Yoshimasa Ishizuka Takami Itoh Shigeru Ikeuchi Masahiko |
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Affiliation: | 1 Department of Life Sciences (Biology), Graduate School of Art and Sciences, University of Tokyo, Komaba, Meguro, Tokyo 153-0041, Japan 2 Division of Material Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan |
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Abstract: | We report the discovery of a novel cyanobacteriochrome, the green/red photoreceptor AnPixJ (All1069), isolated from the heterocyst-forming cyanobacterium Anabaena (Nostoc) sp. PCC 7120. Cyanobacteriochromes are a recently emerging tetrapyrrole-based photoreceptor superfamily that are distantly related to the conventional red/far-red photoreceptor phytochromes (Phys). The chromophore-binding domains of AnPixJ produced in cyanobacterial and Escherichia coli cells both showed a reversible and full photoconversion between a green-absorbing form (λmax = 543 nm) and a red-absorbing form (λmax = 648 nm). Denaturation analysis revealed that the green-absorbing form and the red-absorbing form covalently ligated phycocyanobilin with E-configuration and Z-configuration at the C15C16 double bond, respectively. Time-resolved spectral analysis showed the formation of the first intermediate state peaking at 680 nm from the dark-stable red-absorbing form. This step resembles the first photoconversion step from the red-absorbing form to the red-shifted lumi-R intermediate state of the Phys. These results suggest that the Pr of AnPixJ is almost equivalent to that of the Phys and starts a primary photoreaction with Z-to-E isomerization in a mechanism similar to that in the Phys, but is finally photoconverted to the unique green-absorbing form. |
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Keywords: | Phy, phytochrome Pr, red-absorbing form PCB, phycocyanobilin PAS, Per/ARNT/Sim GAF, cGMP-phosphodiesterase/adenylate cyclase/FhlA PHY, phytochrome-specific 3D, three-dimensional MCP, methyl-accepting chemotaxis protein APr648, red-absorbing form of AnPixJ-GAF2 peaking at 648  nm APg543, green-absorbing form of AnPixJ-GAF2 peaking at 543  nm Pfr, far-red-absorbing form APi680, first intermediate state (APr648-to-APg543) of AnPixJ-GAF2 peaking at 680  nm APi610, second intermediate state (APr648-to-APg543) of AnPixJ-GAF2 peaking at 610  nm CBB, Coomassie brilliant blue R-250 LED, light-emitting diode |
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