An Ethenoadenine FAD Analog Accelerates UV Dimer Repair by DNA Photolyase

作者：Narayanan Madhavan; Singh Vijay R; Kodali Goutham; Moravcevic Katarina; Stanley Robert J^*

来源：Photochemistry and Photobiology, 2017, 93(1): 343-354.

DOI：10.1111/php.12684

Reduced anionic flavin adenine dinucleotide (FADH(-)) is the critical cofactor in DNA photolyase (PL) for the repair of cyclobutane pyrimidine dimers (CPD) in UV-damaged DNA. The initial step involves photoinduced electron transfer from *FADH(-) to the CPD. The adenine (Ade) moiety is nearly stacked with the flavin ring, an unusual conformation compared to other FAD-dependent proteins. The role of this proximity has not been unequivocally elucidated. Some studies suggest that Ade is a radical intermediate, but others conclude that Ade modulates the electron transfer rate constant (k(ET)) through superexchange. No study has succeeded in removing or modifying this Ade to test these hypotheses. Here, FAD analogs containing either an ethano-or ethenobridged Ade between the AN1 and AN6 atoms (e-FAD and epsilon-FAD, respectively) were used to reconstitute apo-PL, giving e-PL and e-PL respectively. The reconstitution yield of e-PL was very poor, suggesting that the hydrophobicity of the ethano group prevented its uptake, while epsilon-PL showed 50% reconstitution yield. The substrate binding constants for epsilon-PL and rPL were identical. epsilon-PL showed a 15% higher steady-state repair yield compared to FAD-reconstituted photolyase (rPL). The acceleration of repair in epsilon-PL is discussed in terms of an epsilon-Ade radical intermediate vs superexchange mechanism.

• 出版日期2017-2