In vivo requirement of integration host factor for nar (nitrate reductase) operon expression in Escherichia coli K-12.
In vivo requirement of integration host factor for nar (nitrate reductase) operon expression in Escherichia coli K-12.
复制标题
大肠杆菌 K-12 中 nar（硝酸还原酶）操纵子表达的体内整合宿主因子的要求。
DOI：
10.1073/pnas.89.18.8701
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发表时间：
1992
影响因子：
11.1
通讯作者：
Stewart,V
中科院分区：
文献类型：
--
作者：
Rabin,RS;Collins,LA;Stewart,V
大肠杆菌的硝酸还原酶操纵子（narGHJI）编码厌氧呼吸酶。先前的工作已经鉴定了nar操纵子控制区中的两个顺式作用位点：由激活剂Fnr介导的厌氧诱导所需的近端位点和由激活剂NarL介导的硝酸盐诱导所需的远端上游位点[Li，S. & DeMoss，J. A.（1988）J.Biol.Chem.263，13700-13705]。我们对nar调控突变体的研究产生了一种在himD（整合宿主因子（IHF）亚基之一的结构基因）中具有突变的菌株。菌株携带无效等位基因的IHF结构基因，himD和himA，有严重的缺陷，硝酸盐诱导的nar操纵子，但正常的硝酸盐诱导的协调调节fdn操纵子。两个操纵子的厌氧表达在突变体中是正常的。凝胶迁移率变化和DNA酶I保护实验揭示了一个单一的IHF结合位点的nar操纵子控制区，位于中间的上游激活位点和启动子。我们的结论是，IHF介导的DNA弯曲是必不可少的有效的硝酸盐诱导的西格玛70依赖的nar操纵子启动子。IHF对转录激活的这种要求已经在几种σ 54依赖性启动子中被注意到。
The nitrate reductase operon (narGHJI) of Escherichia coli encodes an anaerobic respiratory enzyme. Previous work has identified two cis-acting sites in the nar operon control region: a proximal site required for anaerobic induction mediated by the activator Fnr and a remote upstream site required for nitrate induction mediated by the activator NarL [Li, S. & DeMoss, J. A. (1988) J. Biol. Chem. 263, 13700-13705]. Our search for nar regulatory mutants yielded one strain with a mutation in himD, the structural gene for one of the subunits of integration host factor (IHF). Strains carrying null alleles of the IHF structural genes, himD and himA, had severe defects in nitrate induction of the nar operon but were normal for nitrate induction of the coordinately regulated fdn operon. Anaerobic expression of both operons was normal in him mutants. Gel-mobility-shift and DNase I protection experiments revealed a single IHF binding site in the nar operon control region, located midway between the upstream activation site and the promoter. We conclude that an IHF-mediated DNA bend is essential for efficient nitrate induction of the sigma 70-dependent nar operon promoter. This requirement of IHF for transcriptional activation had been noted for several sigma 54-dependent promoters.