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  • Title: Substrate specificity of the ultraviolet-endonuclease from Micrococcus luteus. Endonucleolytic cleavage of depurinated DNA.
    Author: Tomilin NV, Paveltchuk EB, Mosevitskaya TV.
    Journal: Eur J Biochem; 1976 Oct 01; 69(1):265-72. PubMed ID: 991858.
    Abstract:
    The ultraviolet-endonuclease isolated from Micrococcul luteus, specific for pyrimidine dimers, is able to attack not only ultraviolet-irradiated DNA (leading to 3'OH-5'PO4 single-strand breaks) but also superhelical covalently-closed circular DNA of phage lambda damaged by heating at 70 degrees C, pH 5.93. The number of endonuclease-sensitive defects in the DNA corresponds to the number of alkalilabile bonds (apurinic sites) induced by heating. Competition between ultraviolet-induced lesions and apurinic sites for ultraviolet-endonuclease is demonstrated; the affinity of the enzyme for pyrimidine dimers is about three times that for apurinic sites. Both activities of the ultraviolet-endonuclease are inactivated at 50 degrees C at the same rate. The ultraviolet-endonuclease is able to reduce the infectious activity of depurinated lambda DNA towards Ca2+-treated uvr+ and uvr A Escherichia coli cells. It is concluded that both pyrimidine dimers and apurinic sites can be recognized by one and the same enzyme (the ultraviolet-endonuclease).
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