Center for Adaptation Genetics and Drug Resistance, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.
J Bacteriol. 2010 Feb;192(4):942-8. doi: 10.1128/JB.01259-09. Epub 2009 Nov 20.
Bacterial two-hybrid studies of randomly cloned Escherichia coli DNA identified a physical interaction between GyrA, subunit A of gyrase, and MarR, a repressor of the marRAB operon. GyrA-His immobilized on Ni-nitrilotriacetic acid (NiNTA) resin bound MarR, while MarR alone did not bind. GyrA interfered with MarR binding to marO, as detected by electrophoretic mobility assays. In a strain bearing the marRAB operon and a marO-lacZ reporter, overexpression of GyrA increased LacZ activity, indicating decreased repression of marO-lacZ by MarR. These results were confirmed by an increased survival of cells treated with quinolones and other antibiotics when GyrA was overexpressed. This work, like a previous study examining TktA (12), shows that unrelated proteins can regulate MarR activity. The findings reveal an unexpected regulatory function of GyrA in antibiotic resistance.
随机克隆的大肠杆菌 DNA 的细菌双杂交研究鉴定了拓扑异构酶 A（gyrase 的亚基 A）和 MarR 之间的物理相互作用，MarR 是 marRAB 操纵子的阻遏物。固定在 Ni-亚氨基二乙酸 (NiNTA) 树脂上的 GyrA-His 结合了 MarR，而单独的 MarR 则不结合。通过电泳迁移率分析检测到 GyrA 干扰了 MarR 与 marO 的结合。在携带 marRAB 操纵子和 marO-lacZ 报告基因的菌株中，GyrA 的过表达增加了 LacZ 活性，表明 MarR 对 marO-lacZ 的抑制作用降低。当 GyrA 过表达时，用喹诺酮类和其他抗生素处理的细胞的存活率增加，这一结果得到了证实。这项工作与之前研究 TktA（12）的工作一样，表明不相关的蛋白质可以调节 MarR 活性。这些发现揭示了 GyrA 在抗生素耐药性中的一个意想不到的调节功能。
