title: Dynamic Determination of Active-Site Reactivity in Semiquinone Photolyase by the Cofactor Photoreduction.
abstract: 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.
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Zheyun
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Chuang
authors.initials: C
authors.lastname: Tan
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Xunmin
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Jiang
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Dongping
authors.initials: D
authors.lastname: Zhong