Analysis of Autophosphorylating Kinase Activities of Arabidopsis and Human Cryptochromes

Özgür, Sezgin; Sancar, Aziz

doi:10.1021/bi061556n

Cited by 46 publications

(71 citation statements)

References 26 publications

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“…DNA binding. In contrast to the crystal structure of AtCRY1 (Brautigam et al 2004), a computational model of human CRY2 revealed that the DNA-binding groove of photolyase is conserved in human CRYs (Özgür and Sancar 2003). Not surprisingly, human CRY2 bound weakly to double-stranded DNA and with higher affinity to single-stranded DNA nonspecifically (Fig.…”

Section: Biochemical Propertiesmentioning

confidence: 86%

“…7A), with a K D~5 x 10 -9 , and with slightly higher affinity to a single-stranded DNA oligomer containing a (6-4) photoproduct, but there was no photorepair of the lesion. Human CRY1 exhibited similar DNA-binding properties (Özgür and Sancar 2003). Currently, the significance of these findings is not known.…”

Section: Biochemical Propertiesmentioning

confidence: 93%

“…Because of the high sequence and structural similarities between photolyase and CRY, it is generally assumed that CRYs have the same two cofactors as well. However, no CRY has been purified to date from its native source and those that have been purified as recombinant proteins contain FAD to varying levels and either trace amounts of MTHF or none at all (Lin et al 1995;Malhotra et al 1995;Özgür and Sancar 2003;Song et al 2007). Hence, formal proof that CRYs contain MTHF, or any other secondary chromophore, is lacking.…”

Section: Structures Of Photolyase and Cryptochromementioning

confidence: 99%

“…The first group, which includes Arabidopsis CRYs and Insect CRY1s can be purified from bacterial and insect expression systems with essentially stoichiometric amounts of FAD (Lin et al 1995;Malhotra et al 1995;Bouly et al 2003;Özgür and Sancar 2006;). In contrast, the second group, which includes vertebrate CRYs and Insect CRY2s, contains 1-2% FAD and trace amounts of MTHF when purified from bacterial (Hsu et al 1996), insect (Özgür and Sancar 2006;), or mammalian (Özgür and Sancar 2003) expression systems. These findings have raised the legitimate question of whether these CRYs are in fact flavoproteins or whether they have only retained flavin-binding capacity as a functionally irrelevant evolutionary relic.…”

Section: Physical Propertiesmentioning

confidence: 99%

“…Experiments with human CRYs cast some doubt about the role of the weak autokinase activity of CRYs in their function (Özgür and Sancar 2006). First, it was found that no correlation exists between the presence of FAD and the autokinase activity.…”

Section: Protein-protein Interactionsmentioning

confidence: 99%

See 4 more Smart Citations

Structure and Function of Animal Cryptochromes

Öztürk

Song²,

Özgür³

et al. 2007

Cold Spring Harbor Symposia on Quantitative Biology

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Cryptochrome (CRY) is a photolyase-like flavoprotein with no DNA-repair activity but with known or presumed blue-light receptor function. Animal CRYs have DNA-binding and autokinase activities, and their flavin cofactor is reduced by photoinduced electron transfer. In Drosophila, CRY is a major circadian photoreceptor, and in mammals, the two CRY proteins are core components of the molecular clock and potential circadian photoreceptors. In mammals, CRYs participate in cell cycle regulation and the cellular response to DNA damage by controlling the expression of some cell cycle genes and by directly interacting with checkpoint proteins. in response to blue light (Koornneef et al. 1980), was isolated and sequenced, it revealed high sequence homology with Escherichia coli photolyase, and hence, it was in retrospect, correctly speculated that HY4 encoded a blue light photoreceptor and not a signal transducer involved in blue light response (Ahmad and Cashmore 1993). Later, this protein was named cryptochrome 1 (Lin et al. 1995, and a second Arabidopsis protein that has high homology with CRY1 identified by genomics was named CRY2 . The role of CRY in Arabidopsis growth (CRY1) and differentiation (CRY2) was well established by 1995 (see Guo et al. 1998). However, as late as 1997, it was thought that CRY had no role in circadian photoreception in plants (Millar and Kay 1997).The first report implicating CRY in the circadian clock of any organism, plant or animal, came about from the study of DNA repair, in particular, the repair of UV damage in humans by photolyase. This issue had been controversial for nearly 25 years when Li et al. (1993) conducted an exhaustive study with a highly specific and sensitive assay, concluding that humans, like all placental mammals, lacked photolyase (Li et al. 1993). However, a 1995 release of a human expressed sequence tag (EST) list contained a "photolyase ortholog" entry (Adams et al. 1995). In light of this finding and the discovery of a photolyase in Drosophila and rattlesnake (Todo et al. 1993Kim et al. 1996) that repairs the minor UV-induced lesion, the (6-4) photoproduct, in contrast to the classic photolyase that repairs cyclobutane pyrimidine dimers (CPDs), the earlier conclusion regarding the lack of photolyase in humans needed reevaluation. This was done by Hsu et al. (1996) who, in addition to the "photolyase ortholog" in public databases, discovered a second human photolyase gene. Human cells expressing both genes and recombinant proteins encoded by both genes were tested for CPD and (6-4) photolyase activities and were found to lack both. Moreover, the proteins encoded by these genes, like most photolyases (Johnson et al. 1988) and Arabidopsis CRY (Lin et al. 1995; Malhorta et al. 1995), contained FAD (flavin-adenine dinucleotide) and a pterin cofactor. Therefore, it was concluded that these proteins were not repair enzymes but that, like Arabidopsis CRYs, they performed non-repair-related blue light functions and were named human CRY1 and 2 (Hsu et al. 1996). In humans ...

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Section: Biochemical Propertiesmentioning

confidence: 86%

Section: Biochemical Propertiesmentioning

confidence: 93%