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6-4 Photolyase photoantenna

Figure 23.2. Reaction mechanism of PD-DNA photolyase. A photon of blue light is absorbed by the MTHF chromophore that acts as a photoantenna. The excited energy is transferred to the flavin chromophore (FADFF). The excited flavin (FADFI ) acts as a photocatalyst and transfers an electron to a CPD in DNA. The thymines are restored to their native state and the electron is transferred back to the flavin. (Reproduced with permission from Sancar, A. Structure and function of DNA photolyase cryptochrome blue-light photoreceptors. Chem. Rev. 103, 2203-2237, 2003.)... Figure 23.2. Reaction mechanism of PD-DNA photolyase. A photon of blue light is absorbed by the MTHF chromophore that acts as a photoantenna. The excited energy is transferred to the flavin chromophore (FADFF). The excited flavin (FADFI ) acts as a photocatalyst and transfers an electron to a CPD in DNA. The thymines are restored to their native state and the electron is transferred back to the flavin. (Reproduced with permission from Sancar, A. Structure and function of DNA photolyase cryptochrome blue-light photoreceptors. Chem. Rev. 103, 2203-2237, 2003.)...
Fig. 3. Examples of natural photoantenna chromophores (2) 5,10-methenyltetrahydrofolate (MTHF), a blue light photoreceptor pigment present in photolyase and some cryptochromes (3) Pheophytin a, the primary electron acceptor in cyanobacterial oxygenic photosynthesis. (4) 11-cis-retinal, which is involved as sensory photoreceptor component in the opsin-based visual process of animals and (5) the p-hydroxy-benzylidene-imidazolinone chromophore (HBDI) of the green fluorescent protein from bioluminescent marine species. Fig. 3. Examples of natural photoantenna chromophores (2) 5,10-methenyltetrahydrofolate (MTHF), a blue light photoreceptor pigment present in photolyase and some cryptochromes (3) Pheophytin a, the primary electron acceptor in cyanobacterial oxygenic photosynthesis. (4) 11-cis-retinal, which is involved as sensory photoreceptor component in the opsin-based visual process of animals and (5) the p-hydroxy-benzylidene-imidazolinone chromophore (HBDI) of the green fluorescent protein from bioluminescent marine species.
The structure of A. nidulans photolyase is very similar to that of the E. coU enzyme, with one important exception the 8-HDF photoantenna is deeply buried into the interdomain cleft and the center-to-center distance between the two chromophores is 17.5 A. However, the planes of the two chromophores are nearly parallel, allowing for more efficient energy transfer from the second chromophore to FAD, even though they are farther apart than the two chromophores in E. coU photolyase (Rim et al., 1992 Tamada et al., 1997). The T. photolyase has a shorter interdo-... [Pg.79]

The quantum yield of DNA repair by photolyase (the number of cyclobutane pyrimidine dimers split by the enzyme for each photon absorbed by the enzyme in the enzyme-substrate complex) ranges from 0.7 to 1.0. It should be noted, however, that in photolyase FADH is the catalytic cofactor and MTHF (or 8-HDF) is the photoantenna. As a consequence, the quantum yield of photolyase is the product of three reactions (Payne and Sancar, 1990) energy transfer from MTHF (or 8-HDF) to FADH , electron transfer from (FADH ) to the PyrOPyr, and finally splitting of PyrOPyr °. The latter two reactions are very efficient and occur with nearly 100% efficiency, at least in the case of ToT. Therefore, the critical determinant of overall quantum yield of repair is the quantum yield of energy transfer from the photoantenna to the catalytic cofactor (Kim et aL, 1991, 1992). The efficiency of energy transfer by Forster radiationless... [Pg.84]

Photoantennas in the majority of photolyase/cryptochrome blue-light photoreceptors. [Pg.210]


See other pages where 6-4 Photolyase photoantenna is mentioned: [Pg.688]    [Pg.689]    [Pg.497]    [Pg.73]    [Pg.78]    [Pg.80]    [Pg.87]   
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6-4 Photolyase photolyases

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