Cryptochromes

NiNU L, AHMAD M, MiARELLi c, CASHMORE A R and GiULiANO G (1999) Cryptochrome 1 controls tomato development in response to blue light , Plant J, 18, 551-6. 

Folate and FAD are also components of cryptochromes, proteins widespread in living organisms. Cryptochromes are considered photolyase sequence homologues with no DNA repair activities but with blue light-activated factors. Cryptochromes regulate growth and development in plants and seem to be responsible for the synchronization of circadian rhythms in animals and human. ... 

Sancar, A., Structure and function of DNA photolyase and cryptochrome blue-light... 

Sancar, A., Regulation of the mammalian circadian clock by cryptochrome, J. Biol. Chem., 279, 34079, 2004. 

Partch, C. L. et al., Postranslational regulation of mammalian circadian clock by cryptochrome and proteinphosphatase 5, Proc Aarf Acad. Sci. USA, 103, 10467, 2006. Briggs, W.R., Christie, J.M., and Salomon, M., Phototropins a new family of flavinbinding blue light receptors in plants, Antioxid. Redox Signal, 3, 775, 2001. Briggs,W.R. et al.. The phototropin family of photoreceptors. Plant Cell, 13, 993, 2001. 

WADE, H.K., BIBIKOVA, T.N., VALENTINE, W.J., JENKINS, G.I., Interactions within a network of phytochrome, cryptochrome and UV-B phototransduction pathways regulate chalcone synthase gene expression in Arabidopsis leaf tissue, Plant J., 2001, 25, 675-685. 

Ahmad M, Grancher N, Heil M et al 2002 Action spectrum for cryptochrome-dependent hypocotyl growth inhibition in A-rabidopsis. Plant Physiol 129 774—785 Baldwin JM, Schertler GF, Unger VM 1997 An alpha-carbon template for the transmembrane helices in the rhodopsin family of G-protein-coupled receptors. J Mol Biol 272 144—164 Batni S, Scalzetti L, Moody S A, Knox BE 1996 Characterization of the Xenopus rhodopsin gene. J Biol Chem 271 3179-3186... 

Bridges C 1959 The visual pigments of some common laboratory animals. Nature 184 727-728 Burns ME, Baylor DA 2001 Activation, deactivation, and adaptation in vertebrate photoreceptor cells. Annu Rev Neurosci 24 779-805 Cashmore AR, Jarillo JA, Wu Y-J, Liu D 1999 Cryptochromes blue light receptors for plants and animals. Science 284 760-765... 

Rollag MD, Provencio I, Sugden D, Green CB 2000 Cultured amphibian melanophores a model system to study melanopsin photobiology. Methods Enzymol 316 291—309 Sancar A 2000 Cryptochrome the second photoactive pigment in the eye and its role in circadian photoreception. Annu Rev Biochem 69 31—67... 

Young It is not so much a question of what the opsins are doing, but that of the nature of cr3rptochrome, which is a promiscuous protein. When do you expect to find cryptochrome by itself, as opposed to stuck with a dozen or so partners What would you imagine that those partnerships might do to assays of this sort Presumably these in vitro assays that have been done in A rabidopsis and algae have been quite distinct from the in vivo situation. 

Kay Cryptochromes are particularly problematic in matching action spectra to absorption spectra. 

Kay That was a good experiment that Margaret Ahmad did. She over-expressed cryptochrome and then used levels of light that are much lower and which don t initiate a response in the wild-type but do in the over-expressor. This is how she was able to determine a CRYl-specific action spectrum. 

Foster Tony Cashmore has consistently argued that we simply can t know what the absorption spectra of the cryptochromes will be. Others have argued differently. The empirical evidence of a comparison between a flavin absorption spectrum and that of the new CRYl over-expression by Ahmad and colleagues suggests that there is a close correlation. 

Cryptochromes and inner retinal non-visual irradiance detection... 

Generation of retinol-binding protein knockout (Quadro et al 1999), cryptochrome knockout (Thresher et al 1998, Vitaterna et al 1999), and... 

Ketinal-degenerate mice lacking cryptochromes show markedly decreasedphotic sensitivity for behaviour and photic induction of SCNgene expression... 

The decreased behavioural photoresponsiveness in cryptochrome-mutant mice is somewhat difficult to interpret since these mice also lack free-running circadian rhythms. Therefore, one is measuring masking, not circadian responses. Although masking is also preserved in retinal-degenerate animals (Mrosovsky et al 2000), the neural and molecular mechanisms of masking are not as well understood as those of circadian rhythms. 

Retinal-degenerate mice lacking cryptochromes show markedly decreased behavioural photoresponses and pupillary responses, while non-degenerate mice lacking cryptochromes show intact photic signalling... 

Mice lacking cryptochromes and ocular retinal show no photic induction of immediate early genes in the SCN... 

It is theoretically possible that cryptochromes do not function as photopigments, but are required either for the production of another photopigment, or for the signal transduction pathway of another photopigment. Such a pigment would need to be fully resistant to severe vitamin A depletion (since photic immediate-early gene induction in the SCN is fully preserved in RBP I mice but lost in mice) and so is unlikely to be opsin-... 

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