title: Electron transfer mechanisms of DNA repair by photolyase.
abstract: Photolyase is a flavin photoenzyme that repairs two DNA base damage products induced by ultraviolet (UV) light: cyclobutane pyrimidine dimers and 6-4 photoproducts. With femtosecond spectroscopy and site-directed mutagenesis, investigators have recently made significant advances in our understanding of UV-damaged DNA repair, and the entire enzymatic dynamics can now be mapped out in real time. For dimer repair, six elementary steps have been characterized, including three electron transfer reactions and two bond-breaking processes, and their reaction times have been determined. A unique electron-tunneling pathway was identified, and the critical residues in modulating the repair function at the active site were determined. The dynamic synergy between the elementary reactions for maintaining high repair efficiency was elucidated, and the biological nature of the flavin active state was uncovered. For 6-4 photoproduct repair, a proton-coupled electron transfer repair mechanism has been revealed. The elucidation of electron transfer mechanisms and two repair photocycles is significant and provides a molecular basis for future practical applications, such as in rational drug design for curing skin cancer.
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; email: zhong.28@osu.edu.
authors.forename: Dongping
authors.initials: D
authors.lastname: Zhong
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D006801:Humans; D008958:Models, Molecular; D055668:Photochemical Processes; D011487:Protein Conformation; D011740:Pyrimidine Dimers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D011740:Pyrimidine Dimers; C058406:pyrimidine-pyrimidone dimer; D004247:DNA; D004255:Deoxyribodipyrimidine Photo-Lyase
keywords: dimer sequential splitting; electron tunneling pathway; flavin functional state; high repair efficiency; nonequilibrium ultrafast dynamics; proton-coupled electron transfer