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.
Department of Life Sciences (Biology), The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan.
Koji
K
Okajima
Shizue
S
Yoshihara
Yoshimasa
Y
Fukushima
Xiaoxing
X
Geng
Mitsunori
M
Katayama
Shoichi
S
Higashi
Masakatsu
M
Watanabe
Shusei
S
Sato
Satoshi
S
Tabata
Yutaka
Y
Shibata
Shigeru
S
Itoh
Masahiko
M
Ikeuchi
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