Tse-Dinh Y C, McCarron B G, Arentzen R, Chowdhry V
Nucleic Acids Res. 1983 Dec 20;11(24):8691-701. doi: 10.1093/nar/11.24.8691.
E. coli DNA topoisomerase I catalyzes DNA topoisomerization by transiently breaking and rejoining single DNA strands (1). When an enzyme-DNA incubation mixture is treated with alkaline or detergent, DNA strand cleavage occurs, and the enzyme becomes covalently linked to the 5'-phosphoryl end of the cleaved DNA (2). Using oligonucleotides of defined length and sequence composition, this cleavage reaction is utilized to study the mechanism of E. coli DNA topoisomerase I. dA7 is the shortest oligonucleotide tested that can be cleaved by the enzyme. dT8 is the shortest oligo(dT) that can be cleaved. The site of cleavage in both cases is four nucleotides from the 3' end of the oligonucleotide. No cleavage can be observed for oligo(dC) and oligo(dG) of length up to eleven bases long. dC15 and dC16 are cleaved at one tenth or less the efficiency of oligo(dA) and oligo(dT) of comparable length.
大肠杆菌DNA拓扑异构酶I通过瞬时断裂和重新连接单条DNA链来催化DNA拓扑异构化（1）。当用碱或去污剂处理酶-DNA孵育混合物时，会发生DNA链断裂，并且酶与断裂DNA的5'-磷酸末端共价连接（2）。使用具有确定长度和序列组成的寡核苷酸，该切割反应被用于研究大肠杆菌DNA拓扑异构酶I的机制。dA7是测试的可被该酶切割的最短寡核苷酸。dT8是可被切割的最短寡聚（dT）。在这两种情况下，切割位点均位于寡核苷酸3'末端的四个核苷酸处。对于长度达11个碱基的寡聚（dC）和寡聚（dG），未观察到切割。dC15和dC16的切割效率是长度相当的寡聚（dA）和寡聚（dT）的十分之一或更低。
