title: Dynamics and mechanism of cyclobutane pyrimidine dimer repair by DNA photolyase.
abstract: Photolyase uses blue light to restore the major ultraviolet (UV)-induced DNA damage, the cyclobutane pyrimidine dimer (CPD), to two normal bases by splitting the cyclobutane ring. Our earlier studies showed that the overall repair is completed in 700 ps through a cyclic electron-transfer radical mechanism. However, the two fundamental processes, electron-tunneling pathways and cyclobutane ring splitting, were not resolved. Here, we use ultrafast UV absorption spectroscopy to show that the CPD splits in two sequential steps within 90 ps and the electron tunnels between the cofactor and substrate through a remarkable route with an intervening adenine. Site-directed mutagenesis reveals that the active-site residues are critical to achieving high repair efficiency, a unique electrostatic environment to optimize the redox potentials and local flexibility, and thus balance all catalytic reactions to maximize enzyme activity. These key findings reveal the complete spatio-temporal molecular picture of CPD repair by photolyase and elucidate the underlying molecular mechanism of the enzyme's high repair efficiency.
authors.affiliation: Department of Physics, Programs of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA.
authors.forename: Zheyun
authors.initials: Z
authors.lastname: Liu
authors.forename: Chuang
authors.initials: C
authors.lastname: Tan
authors.forename: Xunmin
authors.initials: X
authors.lastname: Guo
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Kao
authors.forename: Jiang
authors.initials: J
authors.lastname: Li
authors.forename: Lijuan
authors.initials: L
authors.lastname: Wang
authors.forename: Aziz
authors.initials: A
authors.lastname: Sancar
authors.forename: Dongping
authors.initials: D
authors.lastname: Zhong
mesh_terms: D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics; D002384:Catalysis; D020134:Catalytic Domain / Q000502:physiology; D004260:DNA Repair / Q000502:physiology*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D011740:Pyrimidine Dimers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D011740:Pyrimidine Dimers; D004255:Deoxyribodipyrimidine Photo-Lyase