Biochemical and functional characterization of BLUF-type flavin-binding proteins of two species of cyanobacteria

Koji Okajima, Shizue Yoshihara, Yoshimasa Fukushima, Xiaoxing Geng, Mitsunori Katayama, Shoichi Higashi, Masakatsu Watanabe, Shusei Sato, Satoshi Tabata, Yutaka Shibata, Shigeru Itoh, Masahiko Ikeuchi

Research output: Contribution to journalArticlepeer-review

115 Citations (Scopus)


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, TII0078 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 TII0078 protein showed slow but reversible aggregation, indicative of light-induced conformational changes in the protein structure. TII0078 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.

Original languageEnglish
Pages (from-to)741-750
Number of pages10
JournalJournal of biochemistry
Issue number6
Publication statusPublished - 2005 Jun
Externally publishedYes


  • BLUF
  • Blue light sensor
  • FAD
  • Photoreceptor
  • Phototaxis
  • Thermophilic cyanobacterium

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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