A novel photoreaction mechanism for the circadian blue light photoreceptor Drosophila cryptochrome

Alex Berndt, Tilman Kottke, Helena Breitkreuz, Radovan Dvorsky, Sven Hennig, Michael Alexander, Eva Wolf

Research output: Contribution to JournalArticleAcademicpeer-review


Cryptochromes are flavoproteins that are evolutionary related to the DNA photolyases but lack DNA repair activity. Drosophila cryptochrome (dCRY) is a blue light photoreceptor that is involved in the synchronization of the circadian clock with the environmental light-dark cycle. Until now, spectroscopic and structural studies on this and other animal cryptochromes have largely been hampered by difficulties in their recombinant expression. We have therefore established an expression and purification scheme that enables us to purify mg amounts of monomeric dCRY from Sf21 insect cell cultures. Using UV-visible spectroscopy, mass spectrometry, and reversed phase high pressure liquid chromatography, we show that insect cell-purified dCRY contains flavin adenine dinucleotide in its oxidized state (FAD(ox)) and residual amounts of methenyltetrahydrofolate. Upon blue light irradiation, dCRY undergoes a reversible absorption change, which is assigned to the conversion of FAD(ox) to the red anionic FAD(.) radical. Our findings lead us to propose a novel photoreaction mechanism for dCRY, in which FAD(ox) corresponds to the ground state, whereas the FAD(.) radical represents the light-activated state that mediates resetting of the Drosophila circadian clock.

Original languageEnglish
Pages (from-to)13011-21
Number of pages11
JournalJournal of Biological Chemistry
Issue number17
Publication statusPublished - 27 Apr 2007


  • Animals
  • Cell Line
  • Circadian Rhythm
  • Cryptochromes
  • DNA Repair
  • Deoxyribodipyrimidine Photo-Lyase
  • Drosophila
  • Drosophila Proteins
  • Flavin-Adenine Dinucleotide
  • Flavoproteins
  • Oxidation-Reduction
  • Photochemistry
  • Photoreceptor Cells, Invertebrate
  • Journal Article
  • Research Support, Non-U.S. Gov't


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