Cyanobacteriochrome TePixJ of Thermosynechococcus elongatus harbors phycoviolobilin as a chromophore |
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Authors: | Ishizuka Takami Narikawa Rei Kohchi Takayuki Katayama Mitsunori Ikeuchi Masahiko |
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Affiliation: | Department of Life Sciences (Biology), The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, Japan. |
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Abstract: | Cyanobacteria have several putative photoreceptors (designated cyanobacteriochromes) that are related to but distinct from the established phytochromes. The GAF domain of the phototaxis regulator, PixJ, from a thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 (TePixJ_GAF) is a cyanobacteriochrome which exhibits reversible photoconversion between a blue light-absorbing form (max = 433 nm) and a green light-absorbing form (max = 531 nm). To study the chromophore, we prepared TePixJ_GAF chromoprotein from heterologously expressed Synechocystis and performed spectral analysis after denaturation by comparing it with the cyanobacterial phytochrome Cph1 which harbors phycocyanobilin (PCB) as a chromophore. The results indicated that the chromophore of TePixJ is not PCB, but its isomer, phycoviolobilin (PVB). It is suggested that the GAF domain of TePixJ has auto-lyase and auto-isomerase activities. |
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Keywords: | Auto-isomerase — Cyanobacteria — Cyanobacteriochrome — Phycocyanobilin — Phycoviolobilin — Phytochrome |
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