A developmentally regulated two-component signal transduction system in Chlamydia
A developmentally regulated two-component signal transduction system in Chlamydia
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DOI：
10.1074/jbc.m212170200
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发表时间：
2003-05-09
影响因子：
4.8
通讯作者：
Stephens, RS
中科院分区：
文献类型：
--
作者：
Koo, IC;Stephens, RS
双组分系统允许细菌适应不断变化的环境条件，并可能诱导生存所必需的发育变化。沙眼衣原体在两种不同的发育形式之间交替，每种形式都在单独的生态位中优化生存。发育的转录调控尚不清楚。沙眼衣原体基因组序列显示，单对基因（ctcB-ctcC）编码的蛋白序列保守于细菌双组分系统。序列分析表明，感应激酶CtcB具有能量感应PAS结构域和磷酸化位点。响应调节因子CtcC与sigma（54）激活因子具有同源性，具有保守的受体和atp酶结构域以及磷酸化位点，但缺乏c端dna结合结构域。ctcB和ctcC在发育周期后期表达，在EB裂解物中均检测到这两种蛋白。从变性大肠杆菌包涵体中纯化重组CtcB和CtcC，并进行折叠。发现CtcC在溶液中以二聚体和四聚体聚集。体外磷酸化实验表明，CtcB在Mg2+、Mn2+和Fe2+存在下发生自磷酸化，在CtcC存在下磷酸化基团转移。总的来说，这些结果表明CtcB和CtcC作为一个双组分系统起作用，并且可能在衣原体发育后期负责sigma（54）全酶的转录调控。
Two-component systems allow bacteria to adapt to changing environmental conditions and may induce developmental changes necessary for survival. Chlamydia trachomatis alternates between two distinct developmental forms, each optimized for survival in a separate niche. Transcriptional regulation of development is not understood. The C. trachomatis genome sequence revealed a single pair of genes (ctcB-ctcC) predicted to encode proteins with sequence conservation to bacterial two-component systems. Sequence analysis revealed that the sensor kinase, CtcB, possessed an energy-sensing PAS domain and phosphorylation site. The response regulator, CtcC, had homology to sigma(54) activators, possessing conserved receiver and ATPase domains and phosphorylation site, but lacked the C-terminal DNA-binding domain. ctcB and ctcC were expressed late in the developmental cycle, and both proteins were detected in EB lysates. Recombinant CtcB and CtcC were purified from denatured Escherichia coli inclusion bodies and refolded. CtcC was found to aggregate as dimers and tetramers in solution. In vitro phosphorylation assays showed that CtcB autophosphorylated in the presence of Mg2+, Mn2+, and Fe2+ and transferred the phosphoryl group in the presence of CtcC. Collectively, these results show that CtcB and CtcC function as a two-component system and are likely responsible for transcriptional regulation by sigma(54) holoenzyme during late-stage chlamydial development.