Cryptochrome family

The TREPR results clearly show that cryptochromes (exemplified for the DASH-type) readily form radical-pair species upon photoexcitation. Spin correlation of such radical-pair states (singlet vs triplet), which is a necessary condition for magnetoselectivity of radical-pair reactions, manifests itself as electron-spin polarization of EPR transitions, which can be directly detected by TREPR in real time. Such observations support the conservation of photo-induced radical-pair reactions and their relevance among proteins of the photolyase/cryptochrome family. The results are of high relevance for studies of magnetosensors based on radical-pair (photo-)chemistry in general [114], and for the assessment of the suitability of cryptochrome radical pairs in animal magnetoreception in particular [17, 115]. 

At this time, the photolyase/cryptochrome family has three members photolyase (cyclobutane pyrimidine dimer photolyase), (6-4) photolyase, and cryptochrome. A number of phylogenetic trees based on sequence comparisons of more than 100 members of the family across the three... 

Fig. 3. Phylogentic relationship among select members of the photolyase/ cryptochrome family. Sequences were aligned with Clustal W, and the tree was produced by the Neighbor-Joining method using MEGA 2.1. Bootstrap confidence values are shown (values for interior branches >95% are statistically significant). At, Arabidopsis thaliana Dm, Drosophila melangaster Ec, Escherichia coli Hs, Homo sapiens Vc, Vibrio cholerae.

Sancar, A., Thompson, C. L., Thresher, R. J., Araujo, F., Mo, J., Ozgur, S., Vagas, E., Dawut, L., and Selby, C. P. (2000). Photolyase/cryptochrome family blue-light photoreceptors use light energy to repair DNA or set the circadian clock. CM Spring Harbor Symp. Quant. Biol. 65, 157—171. 

Worthington, E. N., Kavakli, I. H., Berrocal-Tito, G., Bondo, B. E., and Sancar, A. (2003). Purification and characterization of three members of the photolyase/ cryptochrome family blue-light photoreceptors from Vibrio chokrae. J. Biol. Chem. 278, 3914T-39154. 

Typical photoreceptor proteins are chlorophyllic protein complexes, and proteins belonging to the carotenoid (rhodopsin), phytochrome, and cryptochrome families [10], These function as light-harvesting antenna pigments and auxiliary cofactors in the photosynthetic process, or they may play a regulatory role in biological processes. The chemical structures of typical chromophoric groups contained in these proteins are presented in Table 3.4. 

The Phytochrome Gene Family in Tomato Cryptochromes Family of Tomato Photomorphogenic Mutants of Tomato Photomorphogenic Responses in Different Phases... 

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. 

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... 

Certain flavoproteins act in a quite different role as light receptors. Cryptochromes are a family of flavoproteins, widely distributed in the eukaryotic phyla, that mediate the effects of blue light on plant development and the effects of light on mammalian circadian rhythms (oscillations in physiology and biochemistry, with a 24-hour period). The cryptochromes are homologs of another family of flavoproteins, the photolyases. Found in both prokaryotes and eukaryotes, photolyases use the energy of absorbed light to repair chemical defects inDNA. 

Cryptochrome/photolyase blue light photoreceptor family. The photoreceptors in this family are flavoproteins. They have a wide range of functions including circadian clock regulation, seed germination, and pigment accumulation. 

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