Cryptochrome/photolyase, C-terminal, FAD binding | |||||||||||
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Identifiers | |||||||||||
Symbol | FAD_binding_7 | ||||||||||
Pfam | PF03441 | ||||||||||
InterPro | IPR005101 | ||||||||||
PROSITE | PDOC00331 | ||||||||||
SCOP2 | 1qnf / SCOPe / SUPFAM | ||||||||||
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deoxyribodipyrimidine photo-lyase (CPD) | |||||||||
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Identifiers | |||||||||
EC no. | 4.1.99.3 | ||||||||
CAS no. | 37290-70-3 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
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Photolyases (EC 4.1.99.3) are DNA repair enzymes that repair damage caused by exposure to ultraviolet light. These enzymes require visible light (from the violet/blue end of the spectrum) both for their own activation [1] and for the actual DNA repair. [2] The DNA repair mechanism involving photolyases is called photoreactivation. They mainly convert pyrimidine dimers into a normal pair of pyrimidine bases. Photo reactivation, the first DNA repair mechanism to be discovered, was described initially by Albert Kelner in 1949 [3] and independently by Renato Dulbecco also in 1949. [4] [5] [6]
Photolyases bind complementary DNA strands and break certain types of pyrimidine dimers that arise when a pair of thymine or cytosine bases on the same strand of DNA become covalently linked. The bond length of this dimerization is shorter than the bond length of normal B-DNA structure which produces an incorrect template for replication and transcription. [7] The more common covalent linkage involves the formation of a cyclobutane bridge. Photolyases have a high affinity for these lesions and reversibly bind and convert them back to the original bases. The photolyase-catalyzed DNA repair process by which cyclobutane pyrimidine dimers are resolved has been studied by time-resolved crystallography and computational analysis to allow atomic visualization of the process. [8]
Photolyase is a phylogenetically old enzyme which is present and functional in many species, from the bacteria to the fungi to plants [9] and to the animals. [10] Photolyase is particularly important in repairing UV induced damage in plants. The photolyase mechanism is no longer working in humans and other placental mammals who instead rely on the less efficient nucleotide excision repair mechanism, although they do retain many cryptochromes. [11] Freezing stress in the annual wheat Triticum aestivum and in its perennial relative Thinopyrum intermedium is accompanied by large increases in expression of DNA photolyases. [12]
Photolyases are flavoproteins and contain two light-harvesting cofactors. Many photolyases have an N-terminal domain that binds a second cofactor. All photolyases contain the two-electron-reduced FADH−; they are divided into two main classes based on the second cofactor, which may be either the pterin methenyltetrahydrofolate (MTHF) in folate photolyases or the deazaflavin 8-hydroxy-7,8-didemethyl-5-deazariboflavin (8-HDF) in deazaflavin photolyases. Although only FAD is required for catalytic activity, the second cofactor significantly accelerates reaction rate in low-light conditions. The enzyme acts by electron transfer in which the reduced flavin FADH− is activated by light energy and acts as an electron donor to break the pyrimidine dimer. [13]
On the basis of sequence similarities DNA photolyases can be grouped into a few classes: [14] [15]
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The non-class 2 branch of CPDs tend to be grouped into class 1 in some systems such as PRINTS (PR00147). Although the members of the smaller groups are agreed upon, the phylogeny can vary greatly among authors due to differences in methodology, leading to some confusion with authors who try to fit everything (sparing FeS-BCP) into a two-class classification. [15] The cryptochromes form a polyphyletic group including photolyases that have lost their DNA repair activity and instead control circadian rhythms. [14] [15]
Adding photolyase from a blue-green algae Anacystis nidulans, to HeLa cells partially reduced DNA damage from UVB exposure. [17]
The systematic name of this enzyme class is deoxyribocyclobutadipyrimidine pyrimidine-lyase. Other names in common use include photoreactivating enzyme, DNA photolyase, DNA-photoreactivating enzyme, DNA cyclobutane dipyrimidine photolyase, DNA photolyase, deoxyribonucleic photolyase, deoxyribodipyrimidine photolyase, photolyase, PRE, PhrB photolyase, deoxyribonucleic cyclobutane dipyrimidine photolyase, phr A photolyase, dipyrimidine photolyase (photosensitive), and deoxyribonucleate pyrimidine dimer lyase (photosensitive). This enzyme belongs to the family of lyases, specifically in the "catch-all" class of carbon-carbon lyases.
Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed.
Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and is commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commercial or biological significance, but more complex derivatives are important in biology and biotechnology.
In developmental biology, photomorphogenesis is light-mediated development, where plant growth patterns respond to the light spectrum. This is a completely separate process from photosynthesis where light is used as a source of energy. Phytochromes, cryptochromes, and phototropins are photochromic sensory receptors that restrict the photomorphogenic effect of light to the UV-A, UV-B, blue, and red portions of the electromagnetic spectrum.
Cryptochromes are a class of flavoproteins found in plants and animals that are sensitive to blue light. They are involved in the circadian rhythms and the sensing of magnetic fields in a number of species. The name cryptochrome was proposed as a portmanteau combining the chromatic nature of the photoreceptor, and the cryptogamic organisms on which many blue-light studies were carried out.
Aziz Sancar is a Turkish molecular biologist specializing in DNA repair, cell cycle checkpoints, and circadian clock. In 2015, he was awarded the Nobel Prize in Chemistry along with Tomas Lindahl and Paul L. Modrich for their mechanistic studies of DNA repair. He has made contributions on photolyase and nucleotide excision repair in bacteria that have changed his field.
Pyrimidine dimers represent molecular lesions originating from thymine or cytosine bases within DNA, resulting from photochemical reactions. These lesions, commonly linked to direct DNA damage, are induced by ultraviolet light (UV), particularly UVC, result in the formation of covalent bonds between adjacent nitrogenous bases along the nucleotide chain near their carbon–carbon double bonds, the photo-coupled dimers are fluorescent. Such dimerization, which can also occur in double-stranded RNA (dsRNA) involving uracil or cytosine, leads to the creation of cyclobutane pyrimidine dimers (CPDs) and 6–4 photoproducts. These pre-mutagenic lesions modify the DNA helix structure, resulting in abnormal non-canonical base pairing and, consequently, adjacent thymines or cytosines in DNA will form a cyclobutane ring when joined together and cause a distortion in the DNA. This distortion prevents DNA replication and transcription mechanisms beyond the dimerization site.
Postreplication repair is the repair of damage to the DNA that takes place after replication.
DNA damage-binding protein 2 is a protein that in humans is encoded by the DDB2 gene.
Cystathionine beta-lyase, also commonly referred to as CBL or β-cystathionase, is an enzyme that primarily catalyzes the following α,β-elimination reaction
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DNA photolyase, N-terminal is an evolutionary conserved protein domain. This domain binds a light harvesting chromophore that enhanced the spectrum of photolyase or cryptochrome light absorption, i.e. an antenna. It adopts the rossmann fold.
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(6-4)DNA photolyase is an enzyme with systematic name (6-4) photoproduct pyrimidine-lyase. This enzyme catalyses the following chemical reaction
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