Lemaire Olivier N, Honoré Flora A, Jourlin-Castelli Cécile, Méjean Vincent, Fons Michel, Iobbi-Nivol Chantal
Aix Marseille Univ, CNRS, BIP, 13402 Marseille, France.
Res Microbiol. 2016 Oct;167(8):630-637. doi: 10.1016/j.resmic.2016.05.004. Epub 2016 Jun 8.
Respiration on trimethylamine oxide (TMAO) allows bacterial survival under anoxia. In Shewanella oneidensis, Tor is the system involved in TMAO respiration and it is encoded by the torECAD operon. The torA and torC genes encode TorA terminal reductase and the TorC c-type cytochrome, respectively. Sequence analysis suggests that TorD is the putative specific chaperone of TorA, whereas TorE is of unknown function. The purpose of this study was to understand whether TorD and TorE are two accessory proteins that affect the efficiency of the Tor system by chaperoning TorA terminal reductase. Moreover, by deleting each gene, we established that the absence of TorD drastically affects the stability of TorA, while the absence of TorE does not affect TorA stability or activity. Since TMAO reduction was affected in the ΔtorE mutant, TorE could be an additional component of the TorC-TorA electron transfer chain during bacterial respiration. Finally, a fitness experiment indicated that the presence of TorE, as expected, confers a selective advantage in competitive environments.
氧化三甲胺（TMAO）呼吸作用使细菌能够在缺氧条件下存活。在希瓦氏菌中，Tor是参与TMAO呼吸作用的系统，由torECAD操纵子编码。torA和torC基因分别编码TorA末端还原酶和TorC c型细胞色素。序列分析表明，TorD是TorA的假定特异性伴侣蛋白，而TorE的功能未知。本研究的目的是了解TorD和TorE是否是通过陪伴TorA末端还原酶来影响Tor系统效率的两种辅助蛋白。此外，通过删除每个基因，我们发现缺失TorD会极大地影响TorA的稳定性，而缺失TorE不会影响TorA的稳定性或活性。由于ΔtorE突变体中的TMAO还原受到影响，TorE可能是细菌呼吸过程中TorC-TorA电子传递链的一个额外组成部分。最后，一项适应性实验表明，正如预期的那样，TorE的存在在竞争环境中赋予了一种选择优势。
