amfR, an essential gene for aerial mycelium formation, is a member of the AdpA regulon in the A‐factor regulatory cascade in Streptomyces griseus
amfR, an essential gene for aerial mycelium formation, is a member of the AdpA regulon in the A‐factor regulatory cascade in Streptomyces griseus
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DOI：
10.1046/j.1365-2958.2003.03760.x
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发表时间：
2003-11
影响因子：
3.6
通讯作者：
H. Yamazaki;Y. Takano;Y. Ohnishi;S. Horinouchi
中科院分区：
文献类型：
--
作者：
H. Yamazaki;Y. Takano;Y. Ohnishi;S. Horinouchi
在灰色链霉菌（Streptomyces griseus）中，A因子（2 -异丙基- 3R -羟甲基- γ -丁内酯）作为一种化学信号分子，触发形态分化和次生代谢。在A因子调控级联中，转录激活因子AdpA开启了两个过程所需的许多基因，从而形成了一个AdpA调控子。amfR编码的调节蛋白类似于细菌双组分调节系统的反应调节蛋白，对空气菌丝的形成至关重要，被发现是AdpA调节蛋白的一员。AdpA结合了amfR主要转录起始点- 200位点（位点1）和- 60位点（位点2）的两个核苷酸位置，并通过协助RNA聚合酶在包括转录起始点在内的适当区域形成开放复合物来加速amfR的转录。位点2比位点1对amfR转录激活的贡献更大，尽管AdpA对位点2的亲和力远低于位点1。AdpA增强的amfR转录随后在第2天停止，在野生型菌株中，当空气菌丝开始形成时，而在无adsA突变体中，amfR转录甚至持续到第3天。这表明在σ‐AdsA的控制下，amfR的生长受到基因产物的抑制。amfT上游启动子的转录依赖于amfR，这与amfR作为amf操作子amfTSBA的激活剂的观点是一致的。amfR基因含有一个TTA密码子，这是bldA介导调控的潜在靶标，以及一个保守的Asp - 54残基，可能被一种传感器激酶磷酸化，这表明amfR操纵子受转录、翻译和翻译后控制系统的控制。
In Streptomyces griseus, A‐factor (2‐isocapryloyl‐3R‐hydroxymethyl‐γ‐butyrolactone) acts as a chemical signalling molecule that triggers morphological differentiation and secondary metabolism. A transcriptional activator, AdpA, in the A‐factor regulatory cascade switches on a number of genes required for both processes, thus forming an AdpA regulon. amfR encoding a regulatory protein similar to response regulators of bacterial two‐component regulatory systems and essential for aerial mycelium formation was found to be a member of the AdpA regulon. AdpA bound two sites at nucleotide positions approximately −200 (site 1) and −60 (site 2), with respect to the major transcriptional start point of amfR, and accelerated the transcription of amfR by assisting RNA polymerase in forming an open complex at an appropriate region including the transcriptional start point. Site 2 contributed more to the transcriptional activation of amfR by AdpA than site 1, although AdpA showed a much lower affinity to site 2 than to site 1. The amfR transcription enhanced by AdpA subsequently ceased at day 2 when aerial hyphae began to be formed in the wild‐type strain, whereas in an adsA null mutant amfR was continuously transcribed even until day 3. This implied that amfR was repressed growth dependently by a gene product under the control of σ‐AdsA. Transcription of the promoter upstream of amfT depended on amfR, which is consistent with the idea that AmfR serves as an activator for amfTSBA in the amf operon. The observations that the amfR gene contains a TTA codon, a potential target for bldA‐mediated regulation, and a conserved Asp‐54 residue, which might be phosphorylated by a sensor kinase, suggest that the amf operon is under transcriptional, translational and post‐translational control systems.