Escherichia coli RNase R Has Dual Activities, Helicase and RNase
Escherichia coli RNase R Has Dual Activities, Helicase and RNase
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DOI：
10.1128/jb.01368-09
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发表时间：
2010-03-01
影响因子：
3.2
通讯作者：
Phadtare, Sangita
中科院分区：
文献类型：
--
作者：
Awano, Naoki;Rajagopal, Vaishnavi;Phadtare, Sangita
在大肠杆菌中，当温度从37摄氏度降到15摄氏度时，就会发生冷休克反应，这种反应的特征是在驯化阶段诱导几种冷休克蛋白，包括DEAD盒解旋酶CsdA。CsdA参与多种细胞过程。我们以前的研究表明，CsdA的解旋酶活性对其在细胞冷休克适应中的功能至关重要，并且能够补充其功能的唯一蛋白质是另一种解旋酶RhlE、RNA伴侣CspA和冷诱导的核糖核酸外切酶RNase R。有趣的是，E. coli中的多核苷酸磷酸化酶和RNase II不能补充CsdA的冷休克功能。在这里，我们进行了结构域分析的RNase R，并表明，这种蛋白质有两个不同的活动，RNase和解旋酶，这是相互独立的，是由于不同的结构域。缺乏RNA酶活性但表现出解旋酶活性的突变体RNA酶R蛋白能够补充CsdA的冷休克功能，这表明只有RNA酶R的解旋酶活性对于补充CsdA的冷休克功能是必需的。我们还观察到，在体内删除的两个冷休克结构域导致的能力的RNase R的损失，以补充CsdA的冷休克功能。我们进一步证明了RNase R在体外表现出与其RNase活性无关的解旋酶活性。我们的研究结果揭示了RNase R的独特性质以及它与E.杆菌
In Escherichia coli, the cold shock response occurs when there is a temperature downshift from 37 degrees C to 15 degrees C, and this response is characterized by induction of several cold shock proteins, including the DEAD-box helicase CsdA, during the acclimation phase. CsdA is involved in a variety of cellular processes. Our previous studies showed that the helicase activity of CsdA is critical for its function in cold shock acclimation of cells and that the only proteins that were able to complement its function were another helicase, RhlE, an RNA chaperone, CspA, and a cold-inducible exoribonuclease, RNase R. Interestingly, other major 3'-to-5' processing exoribonucleases of E. coli, such as polynucleotide phosphorylase and RNase II, cannot complement the cold shock function of CsdA. Here we carried out a domain analysis of RNase R and showed that this protein has two distinct activities, RNase and helicase, which are independent of each other and are due to different domains. Mutant RNase R proteins that lack the RNase activity but exhibit the helicase activity were able to complement the cold shock function of CsdA, suggesting that only the helicase activity of RNase R is essential for complementation of the cold shock function of CsdA. We also observed that in vivo deletion of the two cold shock domains resulted in a loss of the ability of RNase R to complement the cold shock function of CsdA. We further demonstrated that RNase R exhibits helicase activity in vitro independent of its RNase activity. Our results shed light on the unique properties of RNase R and how it is distinct from other exoribonucleases in E. coli.