Khachatourians G G
Biochim Biophys Acta. 1979 Feb 27;561(2):294-300. doi: 10.1016/0005-2787(79)90138-2.
[3H]Thymidine (dThd)-labelled Hfr DNA was transferred by conjugation into Escherichia coli F- minicells harvested from an endonuclease I-deficient (endI-) strain and its iosgenic wild type (endI+) parent. The susceptibility of this DNA to attack by DNAase was examined. The kinetics of in vivo conversion of [3H]dThd-labelled DNA into acid soluble radioactivity was examined. This activity, attributed to exonuclease action was the same for both strains. Contribution of endonuclease I was measured by an analysis of changes in weight-average (Mw) and number-average (Mn) molecular weight distribution of DNA molecules recovered from minicells. Reduction in Mw was greater in the endI-strain. The ratio Mn/Mw changed drastically during the incubation period of endI- minicells, but remained unchanged in the endI+ strain. These experiments suggest that the presence of the endI- mutation in minicell-producing strain chi1268 leads to a greater loss in M2 of Hfr DNA conjugally transferred into the minicells.
[3H]胸苷（dThd）标记的高频重组（Hfr）DNA通过接合作用转移到从核酸内切酶I缺陷型（endI-）菌株及其同基因野生型（endI+）亲本收获的大肠杆菌F-小细胞中。检测了该DNA对脱氧核糖核酸酶攻击的敏感性。研究了[3H]dThd标记的DNA在体内转化为酸溶性放射性的动力学。这种归因于核酸外切酶作用的活性在两种菌株中是相同的。通过分析从小细胞中回收的DNA分子的重均分子量（Mw）和数均分子量（Mn）分布的变化来测定核酸内切酶I的作用。endI-菌株中Mw的降低更大。在endI-小细胞的孵育期内，Mn/Mw的比值急剧变化，但在endI+菌株中保持不变。这些实验表明，产生小细胞的菌株chi1268中endI-突变的存在导致通过接合作用转移到小细胞中的Hfr DNA的M2损失更大。
