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Summary of Research Projects (Supports in 2005
Fiscal Year)
| Subjects |
Studies for elucidating the photocycle mechanism of
the novel flavin-based blue-light photoreceptor |
Representative
researcher |
Tokyo Institute of Technology
Shinji MASUDA
|
| Recently, a novel flavin-based photoreceptor
AppA was identified that controls photosynthetic gene expression in response
to both redox state and blue-light intensity in the purple photosynthetic
bacterium Rhodobacter sphaeroides. Its flavin-binding domain,
designated BLUF, have been found on the genome sequences from many eukaryotic
and prokaryotic microorganisms. The photocycle reaction mechanism
of BLUF is unique in the sense that a few hydrogen bond re-arrangements
are accompanied with slight structural changes of bound chromophore. In
this study, we show that the conserved Gln and Trp residues in the BLUF
domain are crucial for the photocycle reaction. Specifically, both
Q63L and W104A mutant AppA are locked in the light-signaling state in
vivo and in vitro. Based on the crystal structures
as well as spectroscopic data from several BLUF-containing proteins, we
conclude that the light-dependent formation/breakage of a hydrogen bond
between Gln63 and Trp104 is crucial for conversion of blue-light signal
into specific apo-protein structural changes to control its anti-repressor
activity. |
|
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