Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

6-4 photolyase repair

Langenbacher, T., Zhao, X., Bieser, G., Heelis, P. F., Sancar, A., and Michel-Beyerle, M. E. (1997). Substrate and temperature dependence of DNA photolyase repair activity examined with ultrafast spectroscopy./. Am. Chem. Soc. 119, 10532—10536. [Pg.98]

Cyclobutane pyrimidine dimer DNA-photolyases (CPD-photolyases) are monomeric DNA repair proteins ( 55 kDa) that directly repair cyclobutane containing UV-light-induced DNA lesionsJ " Another type of photolyases repairs (6-4) lesions. They will be discussed later. The CPD-photolyases are mechanistically the best understood, and three crystal structures of CPD-photolyases fi om E. colij A. nidu-lansf and T. thermophilus provide detailed information about the structural requirements for efficient genome repair. [Pg.2736]

Flavins — Riboflavin is first of all essential as a vitamin for humans and animals. FAD and FMN are coenzymes for more than 150 enzymes. Most of them catalyze redox processes involving transfers of one or two electrons. In addition to these well known and documented functions, FAD is a co-factor of photolyases, enzymes that repair UV-induced lesions of DNA, acting as photoreactivating enzymes that use the blue light as an energy source to initiate the reaction. The active form of FAD in photolyases is their two-electron reduced form, and it is essential for binding to DNA and for catalysis. Photolyases contain a second co-factor, either 8-hydroxy-7,8-didemethyl-5-deazariboflavin or methenyltetrahydrofolate. ... [Pg.113]

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. ... [Pg.113]

Electron donation to nucleobases is a fundamental process exploited by nature to achieve the efficient repair of UV induced lesions in DNA [27, 28]. Nature developed to this end two enzymes, CPD photolyases and (6-4) photolyases, which both inject electrons into the UV damaged DNA bases [29, 30]. Both enzymes are, in many species, including plants, essential for the repair of the UV-light induced DNA lesions depicted in Scheme 1 [31]. [Pg.199]

Scheme 2 Mechanism of repair of cyclobutane pyrimidine dimers (CPD) by a CPD photolyase. 8-HDF 8-hydroxy-5-deazaflavin, ET electron transfer. FADH reduced and de-protonated flavin-coenzyme... Scheme 2 Mechanism of repair of cyclobutane pyrimidine dimers (CPD) by a CPD photolyase. 8-HDF 8-hydroxy-5-deazaflavin, ET electron transfer. FADH reduced and de-protonated flavin-coenzyme...
Flavin-cyclobutane pyrimidine dimer and flavin-oxetane model compounds like 1-3 showed for the first time that a reduced and deprotonated flavin is a strong photo-reductant even outside a protein environment, able to transfer an extra electron to cyclobutane pyrimidine dimers and oxetanes. There then spontaneously perform either a [2n+2n cycloreversion or a retro-Paternd-Buchi reaction. In this sense, the model compounds mimic the electron transfer driven DNA repair process of CPD- and (6-4)-photolyases. [Pg.212]

An in-depth study of DNA repair systems (Aravind et al., 1999a) has concluded that few, if any, repair proteins occur with identical collinear domain arrangements in all three kingdoms of life. Approximately 10 enzyme families of adenosine triphosphatases (ATPases), photolyases, helicases, and nucleases were identified that are all likely to have been present in the cenancestor. These enzymatic domains are accompanied in DNA repair proteins by numerous regulatory domains. This indicates that the domain architectures of these proteins are labile, with incremental addition and/or subtraction of domains to conserved cores to be a common phenomenon except in the most closely related species. [Pg.218]

Carell has recently presented the study of a flavin amino acid chimera to model riboflavin in DNA photolyases [68]. This amino acid LI (Fig. 20) was synthesized in an enantiopure fashion by building the alloxazine ring onto the epsilon amine of lysine. This coenzyme chimera was applied to the problem of repairing DNA damage caused by UV irradiation. LI was incorporated into an 21-residue peptide, P-1, possessing the sequence of the DNA-binding domain of the helix-loop-helix transcription factor MyoD. [Pg.28]

Van Gelder That is the photolyase model. In photolyase, the damaged DNA is bound in the dark, and then dissociates following the light-mediated enzymatic repair of the thymidine dimer. Photolyases are believed to be the molecular ancestors of cryptochromes. [Pg.43]

Kay We have to be very careful about cryptochrome. Cashmore has made the observation that he thinks the cryptochromes are more similar to their own photolyases than to each other, and has used this observation to suggest that cryptochromes have each arisen independently. It is not surprising that cryptochromes could have arisen independently and still be involved in clocks. One of the most stressful stimuli a cell can be exposed to is light. You can imagine one of the first clocks being built around fight dependency of DNA repair. It is wrong to think of cryptochromes as a conserved element of clocks because they could have arisen independently. [Pg.86]

FIGURE 8.2 Formation of a thymine-thymine dimer by UV-B radiation, and repair by UV-A or blue light-activated photolyase. [Pg.402]

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. [Pg.516]

Most microorganisms have redundant pathways for the repair of cyclobutane pyrimidine dimers— making use of DNA photolyase and sometimes base-excision repair as alternatives to nucleotide-excision repair—but humans and other placental mammals do not. This lack of a back-up to nucleotide-excision repair for the removal of pyrimidine dimers has led to speculation that early mammalian evolution involved small, furry, nocturnal animals with little need to repair UV damage. However, mammals do have a path-... [Pg.970]

Direct Repair Several types of damage are repaired without removing a base or nucleotide. The best-characterized example is direct photoreactivation of cyclobutane pyrimidine dimers, a reaction promoted by DNA photolyases. Pyrimidine dimers result from an ultraviolet light-induced reaction, and photolyases use energy derived from absorbed light to reverse the dam-... [Pg.974]

DNA glycosylases 971 AP site 971 AP endonucleases 972 DNA photolyases 974 recombinational DNA repair 976 error-prone translesion DNA synthesis 976 SOS response 976 homologous genetic recombination 978... [Pg.992]

A final check of the fidelity of replication is made after a new strand has been formed. Mismatched base pairs are identified, and the incorrect nucleotides are cut out and replaced by correct ones.655 670 681 683 Some of the thymine dimers created by the action of light are also repaired photochemically by photolyases (see Chapter 23). Photoreactivation was the first DNA repair process recognized.684 However, most thymine... [Pg.1580]

There has been considerable interest in the mechanism of action of DNA photolyase enzymes, which repair pyrimidine dimers in damaged DNA via action of visible light. Several model reactions have given credence to a possible SET pathway. For example, Falvey and coworker reported that the photochemical reaction of dimer 35 with FADH2 results in a retro [2 + 2] cycloaddition according to Scheme 2269. [Pg.1304]

A number of studies are concerned with the free-radical reactions of typical nucleobase lesions. For example, the cyclobutane-type Thy dimer can be split by one-electron reduction [Heelis et al. 1992 reactions (307) and (308)], a process that is relevant to the repair of this typical UV-damage by the photoreactivating enzyme (photolyase, for a review see Carrell et al. 2001, for the energetics of the complex reaction sequence, see Popovic et al. 2002). At 77 K, the dimer radical anion is sufficiently long-lived to be detectable by EPR (Pezeshk et al. 1996). [Pg.308]

The light-induced repair of cylobutane-type dimers by the enzyme photolyase is of major biological importance. This proceeds by ET from a flavin, and using a model system it has been shown that the electron is likely to be funneled through the DNA base stack (SchwOgler et al. 2000). [Pg.426]

Several amphibian species were examined for photolyase activity. This enzyme is responsible for the repair of DNA damage caused by UV-B radiation. A more than... [Pg.474]


See other pages where 6-4 photolyase repair is mentioned: [Pg.199]    [Pg.199]    [Pg.167]    [Pg.48]    [Pg.73]    [Pg.102]    [Pg.197]    [Pg.200]    [Pg.240]    [Pg.264]    [Pg.281]    [Pg.148]    [Pg.28]    [Pg.192]    [Pg.57]    [Pg.66]    [Pg.403]    [Pg.140]    [Pg.974]    [Pg.794]    [Pg.1296]    [Pg.1340]    [Pg.1340]    [Pg.187]    [Pg.476]    [Pg.669]    [Pg.688]    [Pg.371]    [Pg.457]   
See also in sourсe #XX -- [ Pg.88 ]




SEARCH



6-4 Photolyase photolyases

Photolyases

© 2024 chempedia.info