Biochemical and Functional Characterization of BLUF-Type Flavin-Binding Proteins of Two Species of Cyanobacteria

BLUF (a sensor of Blue-Light Using FAD) is a novel putative photoreceptor domain that is found in many bacteria and some eukaryotic algae. As found on genome analysis, certain cyanobacteria have BLUF proteins with a short C-terminal extension. As typical examples, Tll0078 from thermophilic Thermosyn...

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Bibliographic Details
Published in:Journal of biochemistry (Tokyo) 2005-06, Vol.137 (6), p.741-750
Main Authors: Okajima, Koji, Yoshihara, Shizue, Fukushima, Yoshimasa, Geng, Xiaoxing, Katayama, Mitsunori, Higashi, Shoichi, Watanabe, Masakatsu, Sato, Shusei, Tabata, Satoshi, Shibata, Yutaka, Itoh, Shigeru, Ikeuchi, Masahiko
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Proteins - metabolism
blue light sensor
BLUF
Cyanobacteria
Cyanobacteria - metabolism
Cyanophyta
FAD
Flavin-Adenine Dinucleotide - metabolism
Flavins - metabolism
Models, Biological
Molecular Sequence Data
photoreceptor
Photoreceptors, Microbial - chemistry
Photoreceptors, Microbial - metabolism
phototaxis
Protein Structure, Tertiary
Sequence Alignment
Spectrometry, Fluorescence
Synechocystis
Synechocystis - metabolism
thermophilic cyanobacterium
Thermosynechococcus elongatus
Time and Motion Studies
Two-Hybrid System Techniques
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Summary:BLUF (a sensor of Blue-Light Using FAD) is a novel putative photoreceptor domain that is found in many bacteria and some eukaryotic algae. As found on genome analysis, certain cyanobacteria have BLUF proteins with a short C-terminal extension. As typical examples, Tll0078 from thermophilic Thermosynechococcus elongatus BP-1 and Slr1694 from mesophilic Synechocystis sp. PCC 6803 were comparatively studied. FAD of both proteins was hardly reduced by exogenous reductants or mediators except methylviologen but showed a typical spectral shift to a longer wavelength upon excitation with blue light. In particular, freshly prepared Tll0078 protein showed slow but reversible aggregation, indicative of light-induced conformational changes in the protein structure. Tll0078 is far more stable as to heat treatment than Slr1694, as judged from flavin fluorescence. The slr1694-disruptant showed phototactic motility away from the light source (negative phototaxis), while the wild type Synechocystis showed positive phototaxis toward the source. Yeast two-hybrid screening with slr1694 showed self-interaction of Slr1694 (PixD) with itself and interaction with a novel PatA-like response regulator, Slr1693 (PixE). These results were discussed in relation to the signaling mechanism of the "short" BLUF proteins in the regulation of cyanobacterial phototaxis.
ISSN:0021-924X
1756-2651
DOI:10.1093/jb/mvi089