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Dynamic Determination of Active-Site Reactivity in Semiquinone Photolyase by the Cofactor Photoreduction

[Image: see text] Photolyase contains a flavin cofactor in a fully reduced form as its functional state to repair ultraviolet-damaged DNA upon blue light absorption. However, after purification, the cofactor exists in its oxidized or neutral semiquinone state. Such oxidization eliminates the repair...

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Detalles Bibliográficos
Autores principales: Liu, Zheyun, Tan, Chuang, Guo, Xunmin, Li, Jiang, Wang, Lijuan, Zhong, Dongping
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2014
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3985926/
https://www.ncbi.nlm.nih.gov/pubmed/24803991
http://dx.doi.org/10.1021/jz500077s
Descripción
Sumario:[Image: see text] Photolyase contains a flavin cofactor in a fully reduced form as its functional state to repair ultraviolet-damaged DNA upon blue light absorption. However, after purification, the cofactor exists in its oxidized or neutral semiquinone state. Such oxidization eliminates the repair function, but it can be reverted by photoreduction, a photoinduced process with a series of electron-transfer (ET) reactions. With femtosecond absorption spectroscopy and site-directed mutagenesis, we completely recharacterized such photoreduction dynamics in the semiquinone state. Comparing with all previous studies, we identified a new intramolecular ET pathway, determined stretched ET behaviors, refined all ET time scales, and finally evaluated the driving forces and reorganization energies for eight elementary ET reactions. Combined with the oxidized-state photoreduction dynamics, we elucidated the different active-site properties of the reduction ability and structural flexibility in the oxidized and semiquinone states, leading to the dramatically different ET dynamics and photoreduction efficiency in the two states.