Burrington M G, Morgan A R
Can J Biochem. 1978 Feb;56(2):123-8. doi: 10.1139/o78-020.
Although several eucaryote DNA nicking--closing (N--C) enzymes have been characterized, only the Escherichia coli enzyme has been extensively studied amongst procaryotes. The latter enzyme is distinctly different from the eucaryotic enzymes and we have therefore purified the N--C enzyme from Bacillus megaterium to determine if procaryotes form a distinctive class of N--C enzymes. The purified B. megaterium N--C enzyme has a molecular weight of 120,000, only partly relaxes negative supercoils, does not affect positive supercoils, requires Mg2+, and is inhibited by 0.2 M KCl. The enzyme is also inhibited by 1 mM nalidixic or oxolinic acids but unaffected by novobiocin. A crude N--C enzyme preparation from Micrococcus luteus shows very similar properties.
尽管已对几种真核生物DNA切口封闭（N-C）酶进行了表征，但在原核生物中，仅对大肠杆菌的这种酶进行了广泛研究。后一种酶与真核生物的酶明显不同，因此我们从巨大芽孢杆菌中纯化了N-C酶，以确定原核生物是否形成一类独特的N-C酶。纯化的巨大芽孢杆菌N-C酶分子量为120,000，仅部分松弛负超螺旋，不影响正超螺旋，需要Mg2+，并受0.2M KCl抑制。该酶也受1mM萘啶酸或恶喹酸抑制，但不受新生霉素影响。藤黄微球菌的粗制N-C酶制剂表现出非常相似的特性。
