Ogata Y, Mizushima T, Kataoka K, Miki T, Sekimizu K
Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Mol Gen Genet. 1994 Sep 1;244(5):451-5. doi: 10.1007/BF00583895.
The linking number of plasmid DNA in exponentially growing Escherichia coli increases immediately and transiently after heat shock. The purpose of this study was to search for DNA topoisomerases that catalyze this relaxation of DNA. Neither introduction of a topA deletion mutation nor treatment of cells with DNA gyrase inhibitors affected the DNA relaxation induced by heat shock. Thus, DNA topoisomerase I and DNA gyrase are apparently not involved in the process. However, the reaction was inhibited by nalidixic acid or by oxolinic acid in the topA mutant and the reaction was resistant to nalidixic acid in a topA mutant carrying, in addition, the nalA26 mutation. These results are interpreted as indicating that both DNA topoisomerase I and DNA gyrase are involved in the DNA relaxation induced by heat shock.
在指数生长的大肠杆菌中，质粒DNA的连环数在热休克后立即短暂增加。本研究的目的是寻找催化这种DNA松弛的DNA拓扑异构酶。引入topA缺失突变或用DNA促旋酶抑制剂处理细胞均不影响热休克诱导的DNA松弛。因此，DNA拓扑异构酶I和DNA促旋酶显然不参与该过程。然而，在topA突变体中，该反应被萘啶酸或恶喹酸抑制，而在另外携带nalA26突变的topA突变体中，该反应对萘啶酸具有抗性。这些结果被解释为表明DNA拓扑异构酶I和DNA促旋酶都参与了热休克诱导的DNA松弛。
