Structure of a bacterial BLUF photoreceptor: Insights into blue light-mediated signal transduction

Astrid Jung, Tatiana Domratcheva, Marina Tarutina, Qiong Wu, Wen Huang Ko, Robert L. Shoeman, Mark Gomelsky, Kevin H. Gardner, Ilme Schlichting

Research output: Contribution to journalArticlepeer-review

144 Scopus citations


Light is an essential environmental factor, and many species have evolved the capability to respond to it. Blue light is perceived through three flavin-containing photoreceptor families: cryptochromes, light-oxygen-voltage, and BLUF (sensor of blue light using flavin adenine dinucleotide, FAD) domain proteins. BLUF domains are present in various proteins from Bacteria and lower Eukarya. They are fully modular and can relay signals to structurally and functionally diverse output units, most of which are implicated in nucleotide metabolism. We present the high resolution crystal structure of the dark resting state of BlrB, a short BLUF domain-containing protein from Rhodobacter sphaeroides. The structure reveals a previously uncharacterized FAD-binding fold. Along with other lines of evidence, it suggests mechanistic aspects for the photocycle that is characterized by a red-shifted absorbance of the flavin. The isoalloxazine ring of FAD binds in a cleft between two helices, whereas the adenine ring points into the solvent. We propose that the adenine ring serves as a hook mediating the interaction with its effector/output domain. The structure suggests a unique photochemical signaling switch in which the absorption of light induces a structural change in the rim surrounding the hook, thereby changing the protein interface between BLUF and the output domain.

Original languageEnglish (US)
Pages (from-to)12350-12355
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number35
StatePublished - Aug 30 2005


  • Blue light sensing
  • Flavin
  • Photochemistry
  • Protein function
  • Reaction mechanism

ASJC Scopus subject areas

  • General


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