Cryptochrome is a name used for the blue light photoreceptors of plants and animals. The word cryptochrome derives from the Greek κρυπτό χρώμα (krupto chroma), meaning hidden colour. It is now used to describe a specific subset of blue light receptors, a family of flavoproteins that regulate germination, elongation, photoperiodism, and other responses in higher plants. Blue light also mediates phototropism, but this response is now known to have its own set of photoreceptors, the phototropins.

Cryptochromes are highly conserved molecules (evolutionary very old) derived from photolyase, a bacterial enzyme activated by light and participating in DNA damage repair. In eukaryotes the chryptochromes lost their enzymatic activity. Cryptochromes possess two chromophores: pterin and flavin (a chemical relative of pterin). Pterin absorbs a photon, which causes it to emit energy; the latter is absorbed by flavin, which probably mediates the phosphorylation of a certain domain in cryptochrome. This triggers a signal transduction chain that affects gene regulation in the cell nucleus.

Studies in animals and plants suggest that Cryptochromes play a pivotal role in the generation and maintenance of circadian rhythms . In corals they are part of the mechanism that triggers coordinated spawning for a few nights after a full moon in the spring. Cytochromes are also involved in magnetic orientation of birds during migration and essential for the ability of fruit flies to sense magnetic fields.

The genes coding for two Cryptochromes, CRY1 and CRY2, are found on in many species - including in humans on chromosomes 12 and 11.


External links

  • website of Dr. Steven M. Reppert
  • website of the Theoretical and Computational Biophysics Group at the University of Illinois at Urbana-Champaign

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