Kataoka K, Mizushima T, Ogata Y, Miki T, Sekimizu K
Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-82, Japan.
J Biol Chem. 1996 Oct 4;271(40):24806-10. doi: 10.1074/jbc.271.40.24806.
Genetic studies revealed that DNA gyrase seems to catalyze immediate and transient DNA relaxation after Escherichia coli cells are exposed to heat shock (Ogata, Y., Mizushima, T., Kataoka, K., Miki, T., and Sekimizu, K. (1994) Mol. Gen. Genet. 244, 451-455). We have now obtained biochemical evidence to support this hypothesis. DNA gyrase catalyzed an increase in the linking number of DNA and relaxation of negatively supercoiled DNA, under physiological concentrations of ATP. Analyses by gel filtration chromatography of each subunit revealed that DNA relaxation activity co-migrated with each subunit. The linking number of DNA increased as the temperature increased. Further, the reaction was inhibited by nalidixic acid or by oxolinic acid. Based on these results, we propose that DNA gyrase participates in a concerted reaction with DNA topoisomerases in the immediate relaxation of DNA in cells exposed to heat shock.
遗传学研究表明，在大肠杆菌细胞受到热休克后，DNA促旋酶似乎能催化DNA立即发生短暂的解旋（绪方洋、水岛彻、片冈和男、三木彻、关清水，《分子与普通遗传学》，第244卷，第451 - 455页，1994年）。我们现已获得生化证据支持这一假说。在ATP的生理浓度下，DNA促旋酶催化DNA的连环数增加以及负超螺旋DNA的解旋。通过凝胶过滤色谱法对各亚基进行分析发现，DNA解旋活性与各亚基共同迁移。DNA的连环数随温度升高而增加。此外，该反应受到萘啶酸或恶喹酸的抑制。基于这些结果，我们提出，在受到热休克的细胞中，DNA促旋酶与DNA拓扑异构酶协同参与DNA的立即解旋反应。
