McCarthy C, Nester E W
J Bacteriol. 1969 Mar;97(3):1426-30. doi: 10.1128/jb.97.3.1426-1430.1969.
A heat-stable, heat-activated endonuclease was found in sonic extracts of the transformable strain Bacillus subtilis 168 when the organism was grown to logarithmic phase in minimal medium. The enzyme was not present in the poorly transformable strain 23. The endonuclease was stable to 100 C for 30 min and, in a crude extract, was activated by heating at 80, 90, or 100 C. The activation caused a 5- to 10-fold increase in total units of enzyme activity. Sucrose gradient centrifugation indicated that the enzyme in a crude preparation has a major form (molecular weight, 66,000) which remains unchanged after heat activation. Under the assay conditions employed, the endonuclease did not release acid-soluble material from the substrate, high molecular weight tritiated deoxyribonucleic acid. The product, in double-stranded form, had a molecular weight of approximately 10(5), but it appeared to have undergone single-strand breaks.
当可转化的枯草芽孢杆菌168菌株在基本培养基中生长至对数期时，在其超声提取物中发现了一种热稳定、热激活的核酸内切酶。不可转化的23菌株中不存在这种酶。该核酸内切酶在100℃下30分钟仍保持稳定，在粗提取物中，通过80℃、90℃或100℃加热可被激活。这种激活使酶活性的总单位增加了5至10倍。蔗糖梯度离心表明，粗制品中的酶有主要形式（分子量为66,000），热激活后保持不变。在所采用的测定条件下，核酸内切酶不会从底物高分子量的氚标记脱氧核糖核酸中释放出酸溶性物质。产物为双链形式，分子量约为10(5)，但似乎经历了单链断裂。
