Thiara A S, Cundliffe E
Department of Biochemistry, University of Leicester, U.K.
Gene. 1989 Sep 1;81(1):65-72. doi: 10.1016/0378-1119(89)90337-5.
The novobiocin (Nb)-producing organism, Streptomyces sphaeroides, possesses two gyrB genes: gyrBS and gyrBR (encoding the DNA gyrase B subunit-the normal target for Nb) whose products differ in their response to the drug. Novobiocin-sensitive gyrase is the predominant form of the enzyme in this strain and is produced constitutively but at variable levels, whereas Nb-resistant gyrase appears when growth takes place in the presence of the drug. The promoter isolated from the Nb-resistance determinant responds sharply to changes in DNA topology, being activated when the (negative) superhelical density is reduced and vice versa when the supercoiling of DNA is increased. Thus, resistance to Nb in S. sphaeroides is induced by a reduction in DNA supercoiling due to the action of autogenous drug on the sensitive gyrase.
产生新生霉素（Nb）的球形链霉菌拥有两个gyrB基因：gyrBS和gyrBR（编码DNA促旋酶B亚基——Nb的正常作用靶点），其产物对该药物的反应不同。新生霉素敏感促旋酶是该菌株中该酶的主要形式，组成性产生但水平可变，而耐Nb促旋酶在药物存在下生长时出现。从耐Nb决定簇分离的启动子对DNA拓扑结构的变化有强烈反应，当（负）超螺旋密度降低时被激活，反之当DNA超螺旋增加时被激活。因此，球形链霉菌对Nb的抗性是由于自身药物对敏感促旋酶的作用导致DNA超螺旋减少而诱导产生的。
