2007 Fiscal Year Final Research Report Summary
Structural and functional studies on novel photoreceptors and photoregulations in cyanobacteria
| Project/Area Number |
16370018
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
植物生理・分子
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| Research Institution | The University of Tokyo |
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Principal Investigator |
IKEUCHI Masahiko The University of Tokyo, Graduate School of Arts, Professor (20159601)
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| Co-Investigator(Kenkyū-buntansha) |
KATAYAMA Mitsunori Nihon University, College of Industrial technology, Assistant Professor (80345066)
YOSHIHARA Shizue Osaka Prefecture University, Graduate School of science, Assistant Professor (20382236)
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| Project Period (FY) |
2004 – 2007
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| Keywords | Cyanobacteria / Photoreceptors / phytochromes / Phototaxis / BLUE-type |
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| Research Abstract |
In this project, we isolated the holoprotein of SyPixJ1 that is one of the photoreceptors required for positive phototaxis in a unicellular cyanobacterium Synechocystis sp. PCC 6803. We revealed for the first time that SyPixJ1 showed reversible blue/green absorption, which was consistent with the physiological regulation by blue light but was totally unexpected. The chromophore was identified as phycoviolobilin, which is the first evidence for the photoreceptor. BLUF type flavin-binding photoreceptor SyPixD/TePixD was identified as a blue light regulator for positive phototaxis. The X-ray crystal structure of TePixD was determined and the amino acid residue critical for the unique photoreaction was identified by site-directed mutagenesis. By yeast two-hybrid screening, PixE was found as a PixD-interacting factor. The interaction between PixD and PixE was attenuated by blue light irradiation. High light responsive gene sll1621 was detected by DNA microarray analysis and Slr1738 was identified as the redox responsive transcriptional regulator that represses the expression of sll1621 under normal conditions. Three LOV-type photoreceptor genes were studied biochemically and unique sequence features were characterized as a key essential for determination of the light-responsive properties. By site-directed mutagenesis, a unique mutation was introduced into the BLUF-type photoreceptor TePixD to modify the photoreaction that resembles the LOV-type photoreceptor, indicating that a single mutation might change the evolutionary pathways to the distinct photoreceptors.
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