在拓扑异构酶Ⅰ缺失的大肠杆菌突变株中,抑制转录和翻译可以消除高度负超螺旋.为了检测起作用的拓扑异构酶,在拓扑异构酶Ⅰ缺陷的菌株中,以萘啶酮酸抑制旋转酶和拓扑异构酶Ⅳ的活性,结果表明并未影响高度负超螺旋的消除.进一步作了拓扑异构酶Ⅰ,旋转酶,拓扑异构酶Ⅲ和拓扑异构酶Ⅳ的体外松弛实验,结果表明,拓扑异构酶Ⅲ可以松弛高度负超螺旋到正常的超螺旋水平.可以认为拓扑异构酶Ⅲ负责松弛高度负超螺旋并受到某种信号机制的调控. In topoisomerase I-deficient E. coli mutants, inhibition of transcription and translation can eliminate highly negative supercoils.In order to test for the role of topoisomerase, in topoisomerase I-deficient strains, The acid inhibit the activity of spinases and topoisomerase IV and the results showed no effect on the elimination of highly negative supercoils. In addition, topoisomerase I, gyrase, topoisomerase III and topoisomerase IV were further tested in vitro Relaxation experiments showed that topoisomerase Ⅲ could relax highly negatively supercoiled to normal supercoiled level, and topoisomerase Ⅲ could be responsible for the relaxation of highly negative supercoiled and regulated by some signal mechanism.