What is a cryptochrome

Cryptochromes (CRY1 and CRY2) are blue light receptors, which for a long time were only known in plants. Cryptochromes and phototropins from Arabidopsis and other higher plants are well characterized in terms of molecular genetics and biochemistry. Cryptochromes are notable in that they are in vitro can form a flavose quinone radical after light absorption, which not only absorbs blue (short-wave) light but also long-wave light in the green, yellow and red range. Cryptochromes act as photoreceptors that use light to control the plant's internal clock.

In the meantime, cryptochromes have also been detected in animals and bacteria and have been discussed for some time as a circadian photopigment for animal systems. By discovering the genecrybaby, a Drosophila variant of the plant gene cry1 and cry2which is responsible for the production of the protein CRYBABY is responsible, the hypothesis that cryptochrome is involved in the circadian organization became more and more likely. More recent studies (van der Horst et al. 2000) have shown that a mouse needs cryptochromes to ensure normal functioning of the mouse's circadian clock. By blocking the cryptochrome molecules (breaking the DNA sequences - homologous recombination), Van der Horst was able to generate mutant mice that contained the gene cry1, cry2 or they no longer had both genes. The mutants behaved like normal mice under 12 hours of light - 12 hours of darkness (LD 12:12), that is, they were rhythmic in their expressions of life. However, under constant conditions (24 hours of darkness - DD) they showed arrhythmic behavior. From this one could conclude that the cryptochromes were apparently essential for normal clock function. Unfortunately, it is not yet known how cryptochromes interact with other known mouse clock molecules such as Clock, period or Timeless interacts or how the molecular basis of the clock is affected in these mutant mice. CRY1 and CRY2 have been found in mutant mice both in the eyes and in the suprachiasmatic nucleus (SCN) - the seat of the master clock. Hence, one might assume that cryptochromes are responsible for light detection in mammals. However, the facts known up to now speak against the participation of cryptochromes in light detection (Reppert et al.) And at least in favor of the presence of another group of photopigments, the opsins. In mammals, cryptochrome appears to play a central role in watch mechanics itself.

Scientists (Mouritsen et al.) At the University of Oldenburg were also able to detect CRY1 and CRY2 molecules in the retina of migratory birds (garden warbler). Here the molecule is concentrated in special cell types of the retina, which play a role especially in migrating migratory birds; then when the garden warbler orientates itself magnetically. The results of the Oldenburg group support the hypothesis that the cryptochrome could be the magneto-sensory molecule that translates magnetic information into visual signals and therefore enables the bird to perceive the earth's magnetic field with the help of its magnetic sense.

Category: Protein