title: Substrate specificity of the ultraviolet-endonuclease from Micrococcus luteus. Endonucleolytic cleavage of depurinated DNA.
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).
mesh_terms: D001667:Binding, Competitive; D003090:Coliphages; D004279:DNA, Viral / Q000528:radiation effects*; D003851:Deoxyribonucleases / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D004355:Drug Stability; D004720:Endonucleases / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D007700:Kinetics; D008837:Micrococcus / Q000201:enzymology* / Q000528:radiation effects; D011740:Pyrimidine Dimers; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D004279:DNA, Viral; D011740:Pyrimidine Dimers; D003851:Deoxyribonucleases; D004720:Endonucleases