title: Influence of ultraviolet-C on structure and function of Synechococcus sp. PCC 7942 photolyase.
abstract: In this work, an over-expressed cyclobutane pyrimidine dimer (CPD) photolyase of Synechococcus sp. PCC 7942 was used to investigate UV-C (ultraviolet irradiation of C-region) influence on photoreactivation. In vivo photoreactivation experiments indicated that the survival rate decreased from 100 to 2.6% when the UV-C flux was increased from 1.1 to 68.5 muW/cm2. It seemed that the photolyase was easily inactivated at UV-C intensities >or=25.5 muW/cm2. Spectrometric analysis indicated that tertiary structure of the photolyase changed evidently when the UV-C fluxes were >or=25.5 muW/cm2, while the secondary structure was almost unchanged even at 170 muW/cm2. Band shift assay indicated that catalytic activity of the photolyase was impaired at fluxes >or=25.5 muW/cm2, but no significant influence on DNA-binding activity was observed. These results suggest that photoreactivation is efficient at UV-C fluxes <or=25.5 muW/cm2, but would be impaired by intense UV-C irradiation due to structure changes of the photolyase.
authors.affiliation: Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, 100084, P. R. China.
authors.forename: L W
authors.initials: LW
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: Q Y
authors.initials: QY
authors.lastname: Wu
mesh_terms: D002384:Catalysis / Q000528:radiation effects; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000528:radiation effects; D050296:Microbial Viability / Q000528:radiation effects; D017434:Protein Structure, Tertiary / Q000528:radiation effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D046940:Synechococcus / Q000201:enzymology* / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D011994:Recombinant Proteins; D004255:Deoxyribodipyrimidine Photo-Lyase