Purification and characterization of an endonuclease from calf thymus acting on irradiated DNA

An endonuclease acting on DNA exposed to ultraviolet light or gamma-rays has been extensively purified from calf thymus. The enzyme has a pH optimum at pH 7.0-7.5, acts with equal efficiency in the presence of EDTA or divalent cations (Mg-2+ or Ca-2+), is inhibited by NaCl and tRNA and is inactivated by incubation at 50 degrees C. Its molecular weight, determined by Sephadex chromatography or sodium dodecylsulfate gel electrophoresis, is …