title: Characterization of (6-4) photoproduct DNA photolyase.
abstract: Pyrimidine (6-4) pyrimidone photoproduct is the second most abundant UV photoproduct in DNA. Recently, it was reported that Drosophila melanogaster cell-free extracts restored the biological activity of (6-4) photo-product-containing DNA in a light-dependent reaction (Todo, T., Takemori, H., Ryo, H., Ihara, M., Matsunaga, T., Nikaido, O., Sato, K., and Nomura, T. (1993) Nature 361, 372-374) concomitant with the loss of (6-4) photoproduct antigenic sites and (6-4) photoproduct-caused alkali-labile sites. In the present study we show that the (6-4) photoproduct but not its Dewar isomer is the substrate for the enzyme, that the enzyme has an action spectrum peak at 400 nm, and that the efficiency of repair per incident photon is very low compared with cyclobutane pyrimidine dimer photolyases. Furthermore, we provide evidence that the (6-4) photoproduct photolyase converts the photoproduct to unmodified bases probably through an oxetane intermediate.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599-7260.
authors.forename: S T
authors.initials: ST
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Malhotra
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
authors.forename: J S
authors.initials: JS
authors.lastname: Taylor
authors.forename: A
authors.initials: A
authors.lastname: Sancar
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000201:enzymology; D002474:Cell-Free System; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004331:Drosophila melanogaster / Q000201:enzymology; D007536:Isomerism; D008027:Light; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*; D011740:Pyrimidine Dimers / Q000737:chemistry / Q000378:metabolism*; D013053:Spectrophotometry; D013379:Substrate Specificity
chemical_list: D009838:Oligodeoxyribonucleotides; D011740:Pyrimidine Dimers; C058406:pyrimidine-pyrimidone dimer; D004255:Deoxyribodipyrimidine Photo-Lyase