A DNA glycosylase specific for UV radiation–induced pyrimidine dimers has been identified from the Chlorella virus Paramecium Bursaria Chlorella virus-1. This enzyme (Chlorella virus pyrimidine dimer glycosylase [cv-pdg]) exhibits a 41% amino acid identity with endonuclease V from bacteriophage T4 (T4 pyrimidine dimer glycosylase [T4-pdg]), which is also specific for pyrimidine dimers. However, cv-pdg possesses a higher catalytic efficiency and broader substrate specificity than T4-pdg. The latter excises 4,6-diamino-5-formamidopyrimidine (FapyAde), a UV radiation– and hydroxyl radical–induced monomeric product of adenine in DNA. Using gas chromatography–isotope-dilution mass spectrometry and γ-irradiated DNA, we show in this work that cv-pdg also displays a catalytic activity for excision of FapyAde and, in addition, it excises 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua). Kinetic data show that FapyAde is a better substrate for cv-pdg than FapyGua. On the other hand, cv-pdg possesses a greater efficiency for the extension of FapyAde than T4-pdg. These two enzymes exhibit different substrate specificities despite substantial structural similarities.
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1 February 2002
Chlorella Virus Pyrimidine Dimer Glycosylase Excises Ultraviolet Radiation– and Hydroxyl Radical–induced Products 4,6-Diamino-5-formamidopyrimidine and 2,6-Diamino-4-hydroxy-5-formamidopyrimidine from DNA
Pawel Jaruga,
Ritche Jabil,
Amanda K. McCullough,
Henry Rodriguez,
Miral Dizdaroglu,
R. Stephen Lloyd
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Photochemistry and Photobiology
Vol. 75 • No. 2
February 2002
Vol. 75 • No. 2
February 2002