An Endonucleolytic Activity from M. luteus Directed Towards 8-(2-Hydroxy 2-Propyl)-Purines in DNA
An endonuclease directed towards 8-(2-hydroxy 2-propyl) purines in double stranded DNA was discovered in extracts of Micrococcus luteus. The activity does not require divalent cations and it is fully active in 1 mM EDTA, while ATP and caffein cause inhibition. Extracts of mutant M. luteus lacking pyrimidine-dimer “endonucleolytic” activity were found to contain normal levels of the endonuclease. The activity is not inhibited by single stranded DNA, nor by irradiated or depurinated single stranded DNA. Native or depurinated double stranded DNAsdo not cause inhibition whereas UV-(254nm)-or γ-irradiated double stranded DNAs do inhibit the activity hinting at the possibility of a common type of damage in these damaged DNAs. The conformation of 8-substituted purines at the nucleoside and nucleotide level, namely their non-regular syn conformation, suggests that it is the distortion in the DNA which is recognized by the endonuclease. After incision we could demonstrate the specific excision of the 8-alkylated purines from the damaged DNA.
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