Plant and Cell Physiology Advance Access originally published online on September 4, 2008
Plant and Cell Physiology 2008 49(10):1600-1606; doi:10.1093/pcp/pcn132
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Crucial Role in Light Signal Transduction for the Conserved Met93 of the BLUF Protein PixD/Slr1694
1 Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
2 Advancesoft Corporation, Akasaka, Tokyo. 107-0052 Japan
3 Center for Biological Resources and Informatics, Research Center for the Evolving Earth and Planets, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
4 Department of Biomolecular Functional Engineering, Ibaraki University, Hitachi, 316-8511 Japan
*Corresponding author: E-mail, shmasuda{at}bio.titech.ac.jp; Fax, +81-45-924-5823.
| Abstract |
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PixD/Slr1694 from the cyanobacterium Synechocystis sp. PCC6803 is a member of a new class of flavin-containing blue-light sensory proteins containing a BLUF (blue light using flavin) domain. The photocycle reaction mechanism of BLUF is unique because only small structural changes of a bound chromophore are accompanied by a few hydrogen bond rearrangements in the chromophore-binding site. Here, we show that in PixD, Met93, the residue conserved in all BLUF domains, is crucial for light-dependent signal transduction. Specifically, the light-insensitive M93A mutant of PixD revealed biochemical and physiological activities compatible with those of the light-adapted wild-type PixD. However, the W91A mutant of PixD retained light sensitivity and biological function, although the corresponding mutant of another BLUF protein, AppA, has been reported to be locked in the light signaling state. These observations suggest that the pathway through which the light signal is transformed into apoprotein structural changes has been modified in BLUF proteins for their respective functions.
Keywords: BLUF - Cyanobacteria - Flavin - Photoreceptor - PixD
Abbreviations: BLUF, blue-light using flavin; FTIR, Fourier-transform infrared.
(Received August 3, 2008; Accepted September 1, 2008)
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