Cryptochrome

Cryptochromes (from Greek κρυπτός, kryptós, "hidden" and χρωμα, chroma, " color" ) are 50-70 kDa flavoprotein, which may act as photoreceptors for blue light. They were first identified in 1993 in plant and since then also found in bacteria and animals. It contains two non-covalently bound chromophore which flavin adenine dinucleotide (FAD) co-factor, and a light-collecting. They play a role in the maintenance of circadian rhythms in animals and plants and in the magnetoreception - the perception of the geomagnetic field in animals.

Description and function

Cryptochromes are remarkable when, after light absorption can form a Flavosemichinonradikal in vitro, the light not only absorbs in the blue region of the spectrum, but also in green, yellow and red range.

The discovery of the gene in fruit flies crybaby, the cry1 cry2 and is the plant genes very similar and which is responsible for the production of the protein CRYBABY, was the hypothesis that cryptochromes are involved in the circadian organization, and more likely.

Studies (van der Horst et al., 2000 ) showed that a mouse cryptochromes needed to ensure the normal functioning of the circadian clock of the mouse.

By blocking the crypto photochromic molecules ( breaking the DNA sequences - Homologous recombination ) Van der Horst was able to generate mutant mice that no longer possessed the gene cry1, cry2 or both genes. The mutants behaved under 12 hours light - 12 hours dark (LD 12:12 ) as normal mice, that is, they were rhythmically in their expressions of life. However, they were under constant conditions (24 hours dark - DD) arrhythmic behavior. It could be concluded that the cryptochromes were apparently essential for normal clock function. It is not yet known how cryptochrome interacts with other known mouse clock molecules such as clock, period, or Timeless or as the molecular basis of the clock in these mutant mice is affected. CRY1 and CRY2 have been in mutant mice both in the eyes and in the suprachiasmatic nucleus ( SCN ), the seat of the master clock, found. Therefore, one could assume that cryptochromes are responsible for light detection in mammals. However speak far known facts against an involvement of cryptochromes in the light detection ( Reppert et al. ) And at least for the presence of another group of photo- pigments, the opsins. In mammals, cryptochrome seems to play a central role in the Uhrmechanik itself.

For migratory birds, scientists ( Mouritsen et al. ), University of Oldenburg also in the retina detect CRY1 and CRY2 proteins ( garden warbler ). Here the proteins concentrate in specific cell types of the retina, which play a role especially at night attracting migratory birds; So then, when the garden warbler mainly magnetically oriented. The results of the Oldenburg group support the hypothesis that the cryptochrome could be the magneto- sensory molecule that translates the magnetic information into visual signals and allows the bird, therefore, perceive using their magnetic sense the geomagnetic field of the Earth.