Identification, nucleotide sequence, and characterization of PspF, the transcriptional activator of the Escherichia coli stress-induced psp operon
Identification, nucleotide sequence, and characterization of PspF, the transcriptional activator of the Escherichia coli stress-induced psp operon
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DOI：
10.1128/jb.178.7.1936-1945.1996
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发表时间：
1996-04-01
影响因子：
3.2
通讯作者：
Model, P
中科院分区：
文献类型：
--
作者：
Jovanovic, G;Weiner, L;Model, P
大肠杆菌噬菌体休克蛋白（psp）操纵子（pspABCE）在丝状噬菌体感染、乙醇处理、渗透休克、热休克和长时间的固定期孵育等多种应激条件或介质下被强烈诱导。psp操纵子的转录由sigma（54）启动子驱动，并由整合宿主因子刺激。我们在这里报道了一个转录激活基因的鉴定，命名为pspF，它控制着大肠杆菌中psp操纵子的表达。采用随机miniTn10-tet转座子诱变法鉴定pspF基因。将转座子插入到psp基因中可以消除psp操纵子的sigma（54）依赖性诱导。pspF基因与psp操纵子紧密相连，并从一个主要和两个次要的sigma（70）启动子发散转录。pspF编码一个37 kda的蛋白，该蛋白属于sigma（54）转录激活因子的增强子结合蛋白家族。PspF含有一个催化结构域（在其他sigma（54）活化剂中可能是中心结构域）和一个c端dna结合结构域，但完全缺乏一个n端调控结构域，具有组成性活性。插入突变体pspF::mTn10-tet （pspF(877)）编码一个缺失dna结合螺旋-螺旋-螺旋（HTH）基序的截断蛋白（pspF Delta HTH）。虽然中心催化结构域是完整的，但生理浓度的PspF δ HTH不能激活psp的表达。在缺乏诱导刺激的情况下，多拷贝质粒携带的PspF或PspF δ HTH克服了由负调节因子PspA介导的psp操纵子的抑制。
The phage shock protein (psp) operon (pspABCE) of Escherichia coli is strongly induced in response to a variety of stressful conditions or agents such as filamentous phage infection, ethanol treatment, osmotic shock, heat shock, and prolonged incubation in stationary phase. Transcription of the psp operon is driven from a sigma(54) promoter and stimulated by integration host factor. We report here the identification of a transcriptional activator gene, designated pspF, which controls expression of the psp operon in E. coli. The pspF gene was identified by random miniTn10-tet transposon mutagenesis. Insertion of the transposon into the pspF gene abolished sigma(54)-dependent induction of the psp operon. The pspF gene is closely linked to the psp operon and is divergently transcribed from one major and two minor sigma(70) promoters. pspF encodes a 37-kDa protein which belongs to the enhancer-binding protein family of sigma(54) transcriptional activators. PspF contains a catalytic domain, which in other sigma(54) activators mould be the central domain, and a C-terminal DNA-binding domain but entirely lacks an N-terminal regulatory domain and is constitutively active. The insertion mutant pspF::mTn10-tet (pspF(877)) encodes a truncated protein (PspF Delta HTH) that lacks the DNA-binding helix-turn-helix (HTH) motif. Although the central catalytic domain is intact, PspF Delta HTH at physiological concentration cannot activate psp expression. In the absence of inducing stimuli, multicopy-plasmid-borne PspF or PspF Delta HTH overcomes repression of the psp operon mediated by the negative regulator PspA.