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 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.
Okajima
Koji
K
Department of Life Sciences (Biology), The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan.
Yoshihara
Shizue
S
Fukushima
Yoshimasa
Y
Geng
Xiaoxing
X
Katayama
Mitsunori
M
Higashi
Shoichi
S
Watanabe
Masakatsu
M
Sato
Shusei
S
Tabata
Satoshi
S
Shibata
Yutaka
Y
Itoh
Shigeru
S
Ikeuchi
Masahiko
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D000458:Cyanobacteria / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005415:Flavins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013050:Spectrometry, Fluorescence; D046939:Synechocystis / Q000378:metabolism; D013996:Time and Motion Studies; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D005415:Flavins; D020283:Photoreceptors, Microbial; C501329:T11078 protein, cyanobacteria; D005182:Flavin-Adenine Dinucleotide