Mirkin S M, Shmerling Zh G
Mol Gen Genet. 1982;188(1):91-5. doi: 10.1007/BF00332999.
A temperature-sensitive mutant of E. coli with a defective DNA gyrase B subunit has been obtained. The mutation is expressed in the thermolability of DNA gyrase in vitro and in DNA relaxation in vivo. DNA replication in the mutant does not stop under non-permissive conditions; its rate gradually falls by a factor of 2 to 3. The transcription rate also drops by a factor of 2 to 3, but before replication. Small concentrations of rifampicin, an inhibitor of bacterial RNA polymerase, make for a partial survival of the mutant cells under non-permissive conditions. The results suggest the conclusion that DNA supercoiling is mainly required to ensure the optimum transcription level in the cell.
已获得一种大肠杆菌的温度敏感突变体，其DNA促旋酶B亚基存在缺陷。该突变在体外DNA促旋酶的热不稳定性以及体内DNA松弛方面均有体现。在非允许条件下，突变体中的DNA复制不会停止；其速率会逐渐下降2至3倍。转录速率也会下降2至3倍，但发生在复制之前。低浓度的利福平（一种细菌RNA聚合酶抑制剂）可使突变体细胞在非允许条件下部分存活。这些结果表明，DNA超螺旋主要是确保细胞内最佳转录水平所必需的。
