Kaplan J C, Kushner S R, Grossman L
Proc Natl Acad Sci U S A. 1969 May;63(1):144-51. doi: 10.1073/pnas.63.1.144.
Two nucleases that catalyze the excision of photoproducts from UV-irradiated DNA have been extensively purified from M. luteus (M. lysodeikticus). The first enzyme, an endonuclease, has been purified 5000-fold and is free of conflicting nuclease activities. It introduces single-strand breaks into irradiated DNA but does not act on native or single-stranded DNA. The purified enzyme is activated but not dependent on Mg(++) and has an approximate molecular weight of 15,000. Photoproduct excision is absolutely dependent on the second enzyme, a magnesium requiring exonuclease. This enzyme, which has been purified 1000-fold, is devoid of conflicting nucleases. It hydrolyzes irradiated and unirradiated denatured DNA at the same rate, but has no activity on RNA. It only acts on double-stranded DNA which has been both irradiated and pretreated with the endonuclease. The combined action of the endo- and exonuclease results in the quantitative removal of photoproduct regions from UV-irradiated DNA. Approximately five nucleotides are released for every single-strand incision.
已从藤黄微球菌(溶壁微球菌)中大量纯化出两种能催化从紫外线照射的DNA中切除光产物的核酸酶。第一种酶是一种内切核酸酶,已被纯化了5000倍,且没有相互冲突的核酸酶活性。它能在受照射的DNA中引入单链断裂,但对天然DNA或单链DNA不起作用。纯化后的酶被激活但不依赖于Mg(++),其分子量约为15,000。光产物的切除绝对依赖于第二种酶,一种需要镁的外切核酸酶。这种酶已被纯化了1000倍,没有相互冲突的核酸酶。它以相同的速率水解受照射和未受照射的变性DNA,但对RNA没有活性。它只作用于既受照射又经过内切核酸酶预处理的双链DNA。内切核酸酶和外切核酸酶的联合作用导致从紫外线照射的DNA中定量去除光产物区域。每一个单链切口大约释放五个核苷酸。